MCAT Gen Chem Problems & Facts

What is the ratio of neutrons in radon-202 to that in radon-206?

A: 29:30
The number of neutrons for each isotope can be found by subtracting the atomic number of radon (86) from the relevant mass number. Because radon-202 contains (202-86) = 116 neutrons, this gives us a ration of 116:120, which simplifies to 29:30

A particular element overwhelmingly prefers to form one bond and possess three pairs. Which group does this species likely belong in?

A: Group 17
This question is asking the element that has seven valence electrons: one from the bond and six from the lone pairs. Thus it's group 17 with 7 valence electrons.

All of the below statements are true regarding the relationship between oxygen and nitrogen except that

A: Nitrogen has a lower ionization energy than oxygen
Usually, ionization energy increases as it moves towards noble gases; however, the nitrogen-containing group forms an exception to this rule. Nitrogen has an electron configuration of [He]2s^2 2p^3, me

Which of these options correctly list five elements in order of decreasing reactivity with water?

A: Cs, K, Ca, Mg, Be
Reactivity with water is heavily based on ionization energy. Elements with low ionization energy values tend to lose electrons easily, allowing them to rapidly form oxides in water. The list above clearly has the five elements from lo

Properties of transition metals include:
I. the presence of multiple stable oxidation states.
II. the tendency to form brightly-colored gases.
III. the ability to exist in many paramagnetic compounds due to unpaired d-shell electrons.

A: I and III
Transition metals generally possess multiple distinct oxidation states (i.e Mg has oxidation numbers ranging from -3 to +7). They are present in the d block of the periodic table, meaning that many of them do have unpaired d-shell electrons w

What is the electron configuration of Os3+?

A: [Xe]4f^14 5d^5
When determining the electron configuration of a cation, remember that the
highest-energy electrons
should be removed first. Because the 6s subshell possesses the highest principal quantum number, its electrons must also have the most en

Electrons in sample 2 (ultraviolet) could have made which of the following jumps, as indicated by their principal quantum numbers?

A: 4 to 1
To determine the final principal quantum number involved in the transition, we must be familiar with the different series of spectra. The Lyman series (ultraviolet rays) involves any emission with the ground state of electron n=1.
Balmer series

For an arsenic atoms (contains 4 electrons for the outermost) , what is the nuclear charge on an n = 3 and n = 2 electrons?

A: For n =3, 23 & for n =2, 31
Effective nuclear charge is found by subtracting the total number of electrons in all shells preceding the one in question from the nuclear charge (# protons). Arsenic has an atomic number of 32, but we are given As+ with 32

Which of these statements accurately describe the behavior of photoelectrons?
I. A photoelectron's energy can exceed that of the incident photon.
II. A photoelectron's energy cannot equal the energy of the incident photon.
III. The threshold frequency and

A: II and IV
From conservation of energy, the energy of a photoelectron may only be less than the incident photon due to the existence of the work function (energy required for an electron to be released). Because some of the incident photon's energy is d

The combustion of ethanol forms carbon dioxide and water. If 2 moles of ethanol and 4 moles of oxygen are combined in a combustion, the limiting reagent is

A: oxygen
It is not ethanol because we are NOT given a balanced reaction. Once we write a balanced equation, C2H5OH + 3 O2 ? 2 CO2 + 3 H2O; we see that reacting two moles of ethanol requires 6 moles of oxygen.

Given the following elementary reaction, what is the rate law? 3A+B -> 2C

A: Rate = k[A]^3[B]
For elementary reactions, stoichiometric coefficients can be used to write the rate law. These coefficients become exponents according to the following theoretical example: for the reaction aA + bB ? cC, rate = k[A]^a[B]^b.

A student notices that a flask containing several reagents forms ice crystals on its outer surface as they react. He places the flask in a warm bath to prevent further crystal formation. How would this bath affect the new concentration of product at equil

A: The reaction is endothermic; therefore, product concentration should increase
The ice crystal formation indicates that this reaction requires heat energy to proceed; therefore, it must be endothermic. heat can be written as a reactant in this process w

A researcher attempts to maximize the yield of the following reaction:
A (g) + B (g) ? C (s) + D (g) (?H = -92 kJ/mol)
Which of these changes will help accomplish his goal?
I. Increasing the pressure
II. Decreasing the temperature
III. Removing product D

A: I, II, III
I is true because an increase in pressure shifts the reaction to the right because it decreases the number of moles of
gas
as it counteracts the higher pressure.
II- the reaction is exothermic where heat can be written as a product; thus, a

A student in an organic chemistry lab grabs a bottle that supposedly contains an aqueous solution of ammonium phosphate. Unfortunately, he notices thick precipitate lining the sides of the container. Which solution was most likely contaminated with?
A. so

A: Barium nitrate
Ammonium always forms soluble salts. Because we are looking for a substance that forms a precipitate with phosphate, barium cation is a perfect example as it would form barium phosphate, an insoluble compound.

The Ksp of lead iodide is 7.1 � 10^-9. A chemical engineer adds 0.0025 mol of KI to a solution of 0.00004 mol Pb(NO3)2 in 500 mL of water. Should the engineer expect to see a solid precipitate?

A: No, because the ion product is less than the Ksp of lead iodide. Lead diode is PbI2 where Ksp = [Pb2+][I-]^2 with lead and iodide concentrations of 0.00008M (=8
10^-5) and 0.005M (5
10^-3). Therefore, (8 � 10-5)(5 � 10-3)2 = (8 � 10-5)(25 � 10-6). The

Calcium oxalate, a salt found in large amounts in kidney stones, dissociates according to the equilibrium below.
CaC2O4 (s) ? Ca2+ + C2O42- Ksp = 2.7 � 10-9
A student places a chunk of solid calcium oxalate in 10 L of water and notices that a small amount

A: He should add an anion that forms a precipitate with calcium such as hydroxide
B is correct. For this question, consider Le Ch�telier's principle. To increase the concentration of C2O42-, the student must exert a pressure on the system to shift the equ

Which of the following compounds contains a weak Bronsted-Lowry base?
A. Ammonium cation
B. Lithium hydroxide
C. Sodium amide (NaNH2)
D. Potassium acetate

A: Potassium acetate
The acetate anion (C2H3O2-) is the conjugate base of acetic acid as it readily gains a proton to form acetic acid in solution.
- Both B and C are strongly basic
- Ammonium (NH4+) is acidic.. it is ammonia (NH3) that is a classic weak

All of the following statements about Ka and Kb are true except:
A. if the Ka for Acid A is greater than the Ka for Acid B, the pKb of Acid A's conjugate base will be greater than the pKb of Acid B's conjugate.
B. the product of the Ka of HPO42- and the K

Answer: B- The product of the Ka of HPO42- and the kb is equal to the value of Kw at that temperature
When using Ka*Kb = Kw, remember that this is the Ka of the acid with Kb of its conjugate base (NOT the Ka and Kb of the same species). Thus, it is the pe

In aqueous solution, copper ion can react with water molecules to form a vibrant blue complex. This takes place according to the reaction below:
Cu^2+ + 6 H2O ? [Cu(H2O)6]2+
In this reaction, H2O serves as:

A: Lewis base
Since this reaction involves the formation of a bond, we are dealing with the transfer of electrons not the movement of a proton from one molecule to another.
Water (with its two available lone pairs) is able to donate its electrons to coppe

Chloroacetic acid has a pKa of 2.85, while formic acid has a pKa of 3.75. Which of the following statements is true?
A. The Ka of formic acid is larger than the Ka of chloroacetic acid.
B. The Kb of the formate anion is larger than the Kb of the chloroace

Answer: B- The Kb of the formate anion is larger than the kb of the chloroacetate anion
The higher the pKa, the weaker the acid; thus, formic acid is less acidic than chloroacetic acid. Note that weak acids have relatively stronger conjugate bases, and th

The auto-ionization of water is an endothermic process. If the temperature of a beaker of pure water is increased,
A. the water will become acidic.
B. the pH of the water will decrease.
C. Kw will remain unchanged.
D. the pOH of the water will increase.

Answer: B- the pH of the water will decrease
The auto-ionization of water refers to its dissociation into hydronium and hydroxide ions. Auto-ionization is: heat + 2H2O -> H3O+ + OH-. The reaction shifts towards the product in response to increased tempera

A student combines 364.6g of HCl with 80g NaOH in 5L of water. What additional H2O must be added to the mixture to yield a solution with a pH 1?

A: 75L
From here we have 10 moles of HCl and 2 moles of the strong base. When mixed in solution, the base fully neutralizes 2 moles of HCl according to the 1:1 stoichiometric ratio between these reagents.
8 moles of HCl remains in 5L of water. However, we

1.5M tartaric acid (a diprotic acid) is titrated with 0.5M KOH to generate a diprotic titration. If the initial volume of tartaric acid was 750mL, what volume of KOH is required to reach point 2 (1st equivalent point) on the curve?

A: 2.25L
Point 2 is the first equivalence point where we need to add enough KOH to neutralize the
first proton
(
1/2
of the amount required to fully neutralize tartaric acid). We use N1V1=N2V2:(3N tartaric acid)(0.75L) = (0.5M KOH)(x L). Solving for x, we

Zn has an oxidation potential of +0.76, while Al has an oxidation potential of +1.66. Which metal serves as the better oxidizing agent?

A: Zn2+ because it is more prone to gaining electrons
Here, Zn has a less positive oxidation potential; thus, it is less likely to oxidize than Al; however, we switch the signs of the reactions to find their reduction potentials. Zn2+ has a reduction pote

Al3+ has a reduction potential of -1.66 while Cd2+ has a reduction potential of -0.4. In an electrolytic cell at standard conditions

A: Al3+ will reduce at cathode and Cd will oxidize at anode.
Because Al3+ has a more negative reduction potential
than Cd2+, it is Al3+ that will reduce and Cd (s) that will oxidize.
- More negative reduction potential, reduced!

The table below gives the reduction potentials of two metals.
Ag+ + e- -> Ag (E = 0.8V)
Sn2+ + 2e- -> Sn (E = -0.14V)
A system is constructed with two electrodes, one made of solid silver and the other composed of solid tin. Current from an external gener

A: -0.94V
The stem mentions the use of external current to promote this reaction, indicating that it must be nonspontaneous (electrolytic). Thus, the tin cation would reduce (E� = -0.14 V) while the silver metal would oxidize (E� = -0.80 V). (-0.14) + (-0

In the galvanic cell, if the electrode on the left side is the cathode (Ag2SO4 - anode is ZnSO4), which species undergoes the most spontaneous oxidation?

A: Zn(s)
The silver electrode is the cathode. Because the cathode is always the site of reduction, Ag+ reduce to Ag during process; thus, the only oxidation reaction must be Zn(s) -> Zn2+ + 2e-

The Nernst equation: Vm=61/z * log(ion outside/ion inside)
Given that Vm represents the equilibrium membrane potential in mV for a ion and z represents the valence of the ion. In neurons, the overall equilibrium potential is determined almost solely by po

A: K+ outside = 10mM, K+ inside = 149mM
In humans, the resting membrane potential of a typical neuron is approximately -70 mV. For this reason, and since K+ has a valence of +1, we know that the log term in the above equation must be negative. Therefore,

Which of these choices correctly places three nitrogen-nitrogen bonds in order of increasing bond energy?

A: N-N, N=N, N(triple)N
As bond order increases, bond length shortens and bond energy increases.

Which of the following molecules has the highest predicted melting point?
A. H2O
B. CaCl2
C. Ne
D. CH3COCH3

CaCl2
We know that the greater the intermolecular attractions between molecules, the higher the melting point of a sample of those molecules. Given that calcium chloride is a salt that participates in ionic bonds, they have high melting points.
Water has

Of the isomers below, that with the highest boiling point is:
A. 2-methyl-2-butene.
B. trans-2-pentene.
C. 3-methyl-2-butene.
D. cis-2-pentene.

Trans-2-pentene
Boiling point is affected mostly by intermolecular forces and molecular weight. However, these are all hydrocarbon chains. For a hydrocarbon chain, the less branching resembles a more straight change which will "stack" atop like and have h

3.75 moles of nitrogen gas is held in a rubber ballon with a current volume of 1L. The balloon is placed in a room with an initial pressure of 1 atm and temperature 25 celcius. If the pressure drops to 0.75 atm, which change in volume is necessary if the

A: The volume must be increased to 1.33L
We can use Boyle's law P1V1=P2V2 given (1atm)(1L)=(0.75atm)(X), the new volume must be 1.33L

The heat of vaporization of water is 2256kJ/kg, while the heat of fusion is 334 kJ/kg. What amount of heat is required to fully convert 120g of ice at 0 degree into water, also at 0 degree?

a: 40080J
Here, we want to use the heat of fusion not vaporization. Note that Q=McT only works when temperature is changing; thus, for phase transitions, we use Q=mL where L is the latent heat.
In this, we have (0.12Kg)(334KJ/Kg), which equals 40000J

A restaurant manager wants to melt 10 kg of ice at -8�C into water at 20�C. If his restaurant has an ambient pressure of 1 atm, how much heat will the entire process require? Note that cice = 2.03 J/(g?�C), cwater = 4.18 J/(g?�C), and Hfusion (water) = 33

A: 4.3*10^6 j
This process must be broken down into steps. First, ice at -8�C becomes ice at 0�C. Plugging known values in to Q = mc?T yields Q = (1 � 104 g)(2.03 J/(g?�C))(8�C) = 1.6 � 105 J. Next, ice at 0�C is melted to form water at the same temperatu

1.25 mol of Ca(NO3)2 is added to exactly 0.25 kg of water. If the Kf of water is 1.86 �C ? kg / mol, what will the solution's new freezing point be?

A: -28 celcius
Freezing point depression can be calculated using ?Tf = Kfmi, where Kf is a constant, m is molality, and i is the Van't Hoff factor, or number of dissolved particles per molecule. Here, m is (1.25 mol) / (0.25 kg) = 5 m, while i = 3. ?Tf =

As increasing amounts of NaCl are added to water

A: Boiling point will increase, melting point will decrease, and vapor pressure will decrease
Colligative properties include boiling point elevation, melting (freezing) point depression, and vapor pressure depression. As more solute is added, these proper

If one mole of sucrose depresses the freezing point of a certain volume of water by 3.9 degree, what would be the freezing point of the same volume of water when one mole of malonic acid is added?

A: -11.7 degree
Because freezing point depression is a colligate property, it depends on the number of particles in solution. Sucrose is organic and doesn't dissolve in water but carboxylic acids lost a proton at pH ~7; thus, malonic acid dissociates into

What is the approximate partial pressure of oxygen at 1500m?

A: 0.18 atm
Table in the passage shows the barometric pressure at 1500m = 641 mmHg or 85 kPa.
Remember the conversion
1 atm = 760 mmHg = 10^5 Pa; thus, we conclude that the pressure at 1500m is 0.84atm. The passage also states that air is 21% oxygen, mean

The hemoglobin (Hb) dissociation curve at high altitude has a distinct sigmoidal shape from that at atmospheric pressure. Which of the following best explains this shape?

A: Homotropic regulation by oxygen occurs
The sigmoidal shape of the curve implies that as each oxygen molecule binds to Hb, the affinity of Hb for oxygen goes up. Homotropic regulation is when a molecule serves as a substrate for its target enzyme as wel

Fluid pressure changes with depth are assumed to be linear. Which statement best explains which this does not hold true for atmospheric pressure changes?

A: The volume of a mass of air is not constant
Hydrostatic pressure for liquids is linear because as depth changes, the density of liquid remains constant. Gases, however, are compressible and have densities that change according to the forces applied to

Which of the following most closely approximates the pKa of phenolphthalein?

A: 9.3
Indicators undergo a color change near the desired
pH
; this typically occurs because of a reversible change in the protonation state of the indicator. It's desirable that the
pKa
of a chosen indicator is within +/- 1 of the target pH.
For the titr

An additional experiment on the bovine extracts using a known ADAMTS inhibitor would serve as

A: A positive control
A positive control is a control group not exposed to the experimental treatment but exposed to some other treatment that is KNOWN to produce the expected effect. In this passage, the scientists wished to test the effect of the analog

Which of the following phase changes are exothermic processes?
I. Liquid to gas
II. Liquid to solid
III. Gas to solid

A: II and III
Gases have more heat energy than liquids and liquids have more heat than solids. Thus, II and III are exothermic.
- I is endothermic (i.e need to invest heat energy to equilibrate and change liquid -> gas)

When 2 moles of hydrofluoric acid are added to 100mL of water, the resulting solution has a pH ~4. What is the percent dissociation of HF?

A: 0.0005%
Remember that HF is a weak acid that doesn't fully dissociate in water.
This question gives pH: pH = -log[H+]; therefore, [H+] = 10^-pH where [H+] = 10^-4 M. "Percent dissociation" indicates the percent of the original acid concentration that h

What would be the approximate ratio of lactate to lactic acid in the final lactated ringer's solution after the initial preparation by Student A?

A: 1000:1
The Henderson-Hasselbalch equation is used to solve for the ratio of the conjugate base (lactate) to the acid (lactic acid) in a buffer solution of known pH. According to the equation, pH = pka + log[A-]/log[HA] where [A-]/[HA] = 10^(pH-pKa). pH

Which compound precipitated in trial 3 of experiment 2 from student A and failed to precipitate in trial 3 of experiment 2 from student B?

A: FeF2
To determine which compounds will precipitate, it's necessary to compare the
reaction quotient (=ion product) Q
to the Ksp.
If Q < Ksp, no precipitate will form
if Q = Ksp, the solution is saturated
if Q > Ksp, precipitate will form
Here, Fe(OH) 2

The osmolarity of blood is approximately 298 mOsm. What is the difference in osmotic pressure between the blood and lactated Ringer's solution at standard temperature?

A: 50 Pa
The osmotic pressure can be found by the equation n=MRT. To find the total molarity of lactated Ringer's solution, simply add up the concentrations of ALL ions shown (sodium + chloride + lactate + potassium + calcium) = 0.2725 Osm. We are given t

Air is bubbled through distilled water. The solution will have a pH

A: Less than 7, because carbon dioxide undergoes hydrolysis
Air contains elemental nitrogen as its major component, but elemental nitrogen is essentially INERT and is NEITHER an acid/base. On the other hand, carbon dioxide undergoes a hydrolysis reaction

What is the approximate pH of a saturated aqueous solution of hydrochloric acid whose molarity is 10.6M?

A: -1
Hydrochloric acid is a strong acid that completely dissociates in aqueous solution. In this problem, the hydronium ion concentration is 10.6M. The pH is the -log of the hydronium ion concentration: -log[10] = -1.
- Note that it's possible to have a

If trifluoroacetic acid is the reagent used in SP synthesis, which of the following would be the most effective for creating an effective support system?
A.NH3
B.NaOH
C.p-bromophenol
D.Benzene

A: Benzene
The passage indicates that an ideal support must be inert to all reagents and solvents used during SP synthesis. This tells you that we are using a weak acid; we want a molecule that will be inert to the actions of an acid. Benzene, an aromatic

Which of the following relationships must hold? (note 1m^3 = 1000L)

A: 100 kPa is equivalent to 100J/L
This is a unit conversion problem!
100 kPa = 100,000 Pa = 100,000 N/m2 = 105 N/m2
100 J/L x (1000 L/m3) = 105 J/m3 = 105 Nm/m3 = 105 N/m2

Which of the following electronic transitions for a hydrogen atom would result in the emission of a photon that would be visible to the human eye?

A: n=4 to n=2
The visible spectrum contains electromagnetic signals with wavelengths ranging 400-700nm. The wavelength of light emitted during a particular electronic transition determined by the energy difference between the initial and final energy leve

The transition from N to O offers an exception to the trend for first ionization energy due to Hund's rules of spin pairing. If this spin pairing wasn't present, what would be the expected first ionization energy for the p-orbital on an oxygen atom?

A: 1700 kJ/mol
In the figure from the passage, we see a dip between group 5 (N) and group 6 (O). If we examine the trend for the first 6 elements, IE goes from 500 (Li) to 1500 (N), giving a slope of about 200kJ/mol per. This trend would have continued, i

A hospital purchases brand-new GKS-Co and GKS-X machines. Five years after installation, what is the expected ratio of the total atomic mass of radioactive material (both before and after decay) in the Co machine to that in the X machine, assuming both ma

A: 1:1
This question is NOT asking about the percentage of an isotope left after radioactive decay. Instead, it is asking about atomic mass. B-decay does cause a nuclear transmutation of protons to neutrons or vice versa, the atomic mass lost in these pro

Free radicals from ionizing radiation are highly unstable and have carcinogenic effects that are likely result from damage to

A: Nucleic acids
Free radicals can cause cancer, which is a result of poorly regulated cell growth and division. Cancer is generally a product of mutations in DNA that disrupt these processes.
Cancer is always related to GENETIC MUTATION

What of the following types of electromagnetic radiation would have the shortest wavelength?

A: Radiation that ejects an electron from an sp orbital
Shorter-wavelength EMR (like gamma rays) carries much more energy than longer wavelength. Thus, we should look for the highest-energy EMR. The closer an electron is to the nucleus, the harder it is t

How much heat is produced from the complete combustion of 30.0 g of methane, if the enthalpy of reaction is -890 kJ/mol?

A: 1.7 * 10^6 J
Methane has a molecular formula of CH4 with its molecular weight 16g/mol.
30g CH4
(1 mol/16g)
(890kJ/mol) = 1.7*10^6 J

More complete fractionation of proteins using an Size-exclusion chromatography (SEC) column could be achieve by using a

A: longer column
Like other chromatographies, increasing the column length enhances the resolution of the column, leading to more completion fraction by SEC by providing the physical means of separating the proteins.

What is the pH of a 0.10 M aqueous solution of acetylsalicylic acid?

A: 2.3
Acetylsalicylic acid is a weak acid with pKa 3.5. Thus, the pH of this solution must be less than the pKa because the compound is in its acid form and pH of 3.5 would mean that the concentration of weak acid and conjugate base were equal (a buffer)

What is the net charge on a phenylalanine molecule at pH 1?

A: +1
Being an amino acid, phenylalanine has an acidic carboxy group that will be protonated at a pH of 1 (remember, such a pH is highly acidic). Additionally, it has a basic amino group that will also be protonated. Finally, it contains a neutral toluene

Which of the following electronic transitions for hydrogen would result in the emission of a quantized amount of energy?

A: n=5 -> n=4
In order to emit a PHOTON of energy (QUANTIZED), an electron must go from a higher energy level to a lower energy level

During strenuous exercise, lactic acid buildup in cells causes the creation of a hydronium complex known as the Eigen cation (H9O4+). If water molecules then experience hydrogen bond attractions to the Eigen cation, this attractive force:

A: Results in a semi-stable shell of water molecules around the hydronium
Process known as "hydration" or "solvation" occurs when the attractive force of an ion molecule causes a think shell of water molecules to surround it. For hydronium, each of the H

Efforts to treat lactic acid buildup in muscles were attempted using dissected muscle specimens in the laboratory. One of these experiments involved ammonium formation from dissolved ammonia. Under conditions of excessive lactic acid:

A: The final concentration of ammonium will be higher than otherwise due to lower pH
In acidic environment, a base such as ammonia (NH3) dissolves into ints conjugate acid ammonium (NH4+) to a greater extend that would have been in a neutral/basic environ

If sodium sulfate was added to the mixture containing silver ions and the yellow precipitate, in theory it could lead to the precipitation of silver sulfate. Which of the following might correctly explain what might be observed after a significant amount

A: Little to no silver sulfate formation because the Ksp of silver sulfate is very large compared to the Ksp of the yellow precipitate
The Ksp, or solubility product, of a substance is defined as the product of each of the substance's dissolved ion concen

Which of the following best explains why arginine is more basic than lysine?

A: The electron-donating groups around the basic nitrogen on arginine make its conjugate acid more stable
Since, in its protonated form, arginine has electron-donating groups via resonance with other nitrogens; it is a more stable conjugate acid.

If an archaebacteria species lives in a pool that is 0.01M HCl(aq), what is the pH of the water?

A: 2
The pH of a solution is -log[H+]. The strong acid HCl completely dissociates in water; thus, an HCl concentration of 0.01M means that the H+ concentration is 0.01M (10^-2 M); pH is 2
Q2. What is the pH of a 0.001M NaOH solution?
A: 11
A 0.001M NaOH s

If a leak develops in the vacuum distillation apparatus, the boiling points of the two components of caraway seed oil will

A: Both increase
The boiling point of a liquid is the temperature at which
the vapor pressure of the liquid equals the surface pressure
. The normal boiling point is measured at 1atm pressure. The vapor pressure of a liquid increases with increasing tempe

If red litmus paper is dipped into the Na2CO3 solution, it will

A: Turn blue, because carbonate reacts with water to produce OH-
In water, carbonate will undergo the following reaction: CO3^2- + H2O -> HCO3 + OH-. Red litmus paper will turn blue in a base!

What happens when HCl reacts with CO3^2-?

When HCl is added and reacts with CO3^2-, it forms CO2(g)

What does the solution containing nickel(II) ions green colored?

The color arises because nickel(II) ion has partially filled d orbitals and the electrons in the lower energy d orbitals absorb visible light to move to the higher energy d orbitals

Which of the following experimental modifications will most likely improve the degree of separation between limonene and (+)-carvone?

A: Heating the distillation flask at a slower rate
(I picked: "Using a vacuum source that can achieve a lower pressure inside the distillation apparatus")
The separation of the two liquids takes place in the fractionating column as the two liquids vaporiz

According to equation 1, the concentration of the polymer with respect to [HPO4^-2] is

A: (1/n)[HPO4^2-]
Equation 1: nCDP -> (CP)n + nHPO4^2-
According to the balanced coefficients, each time one molecule of the polymer (CP)n is formed, there also are n hydrogen phosphate ions HPO4^-2 produced. Therefore, the concentration of (CP)n must be

What is the sum of the protons, neutrons, and electron in strontium-90?

A: 128
In a neutral atom, the number of electrons is equal to the number of protons. The number of neutrons can be found by subtracting the atomic number from the mass number. The atomic number of strontium (Sr) is 38; thus, the number of neutrons is 52.

Alcohols generally require acid catalysis in order to undergo substitution by nucleophiles. The acid catalyst enhances the reaction by

A: Creating a better leaving group
Remember that the substitution reaction serves to replace the hydroxyl group and hydroxide ion is one of the worst leaving groups in substitution reactions. Under acidic conditions, the hydroxyl group is protonated such

Ignoring stereochemistry, how many different tripeptides may exist that contain the same three amino acids as the molecule shown below?

A: 6
The formula for the number of possible peptides that contain one each of n amino acid is
n!
. Given compound has n=3, thus, the answer is 6.
For a tripeptide ABC, the following combinations are possible: ABC, ACB, BAC, BCA, CAB, and CBA

Would deviations from the ideal gas law be observed for gaseous nitrogen at 180GPa and room temperature?

A: Yes, because at this pressure, molecular volumes and intermolecular forces become significant
According to the passage, the solid form of nitrogen is stable above 65 GPa. The ideal gas law assumes that molecular volumes and intermolecular attractive fo

What is the best explanation for the fact that a solution of NaNO2(aq) is basic?

A: NO2- is hydrolyzed with the formation of OH- (aq) ions
NO2- reacts with water, forming OH- ions

Which of the following properties is associated with the existence of glycine as a dipolar ion in aqueous solution?

A: High dipole moment
Polarity in neutral molecules results from an uneven distribution of electron density, which can arise from separation of unlike charges (this occurs in zwitterions and ylides). Additionally, molecules containing strongly electron-wi

Na2CO3 + HCl -> CO2 + H2O + NaCl
Consider the above unbalanced equation. For this reaction, how many mL of a 2M solution of Na2CO3 are required to produce 11.2L of CO2 at STP?

A: 250mL
First, we must balance the equation:
Na2CO3 + 2HCl -> CO2 + H2O + 2NaCl
Because one mole of an ideal gas at STP occupy a volume of 22.4L, 11.2L of CO2 gas at STP must represent 0.5 mole of CO2. Because of the mole ratio, one mole of CO2 is produc

Which of the following formulas represents a general structure of a fatty acid salt produced in reaction 1 (saponification)

A: Rn-CO2- Na+
A fatty acid has the general formula Rn-CO2H. The corresponding fatty acid salt has the general formula Rn-CO2- Na+

Which of the following is the most plausible explanation for the fact that the saponification of the triacylglycerol in the passage resulted in 4 different fatty acid salts?

A: One of the fatty acid salts was unsaturated, and a small percentage isomerized under the reaction conditions
(I picked: "one of the fatty acid salts was unsaturated, and it completely isomerized under the reaction conditions")
If one of the R groups in

How much sodium hydroxide is needed to completely saponify a triacylglycerol?

A: Three equivalents, because one OH- ion is required to saponify each of the three fatty acid groups
One hydroxide ion is required to hydrolyze one ester linkage of a triacylglycerol molecule. Because there are three ester linkages in a triacylglycerol,

Which of the following statements most accurately describes the solubility properties of fatty acid salts?

A: They can partially dissolve in both polar and nonpolar media
(I picked: "They are soluble in polar media only")
The fatty acid salt contains a long hydrocarbon chain, which is soluble in nonpolar solvents. The salt contains the charged group -CO2- NA+,

What is the molar concentration of Na+ (aq) in a solution prepared by mixing 10mL of 0.01M NaHCO3 (aq) solution with 10mL of 0.01M Na2CO3(aq) solution?

A: 0.015 mole/L
Since 1 equivalent NaHCO3 provides 1 equivalent of Na+, the molar concentration of Na+(aq) in 0.01M NaHCO3(aq) solution is also 0.01M = 0.01 mole/L. The molar concentration of Na+ (aq) in 0.01M Na2CO3 provides 2 equivalents of Na+. When eq

Which of the bromomethanes is least polar
A. CBr4
B. CHBr3
C. CH2Br2
D. CH3Br

Answer: A (I picked D)
The polarity of each of the bromomethanes is determined by the vector sum of all of the individual bond polarities within a given molecule of the compound. Carbon is sp3 hybridized and tetrahedral in all of the bromomethanes. Thus,

In equation 1, HPO4^2- is the conjugate

A: base of H2PO4-
A base differs from its conjugate acid only in the lack of a single H+
Q2. What is the conjugate base of chlorobenzoic acid?
A: C7H4ClO2-
Conjugate acids and bases differ only by the presence/absence of a proton H+. The conjugate base of

Experiment 1 was repeated with 0.4g of calcium, and the gas that evolved was collected. The identity of the gas and its approximate volume at 1atm and 27 celcius were

A: H2, 250mL
Calcium undergoes the following reaction with water:
Ca(s) + 2H2O(l) -> Ca2+ + 2OH- + H2
The gas produced was H2. If 0.4g calcium reacted, the moles of calcium reacted was 0.01mol; the amount of H2 formed was also 0.01 mol.
The volume of 0.01

To a first approximation, the ionization constant of H2S is

A: Much less than 1
H2S is a weak acid that dissociates in water but only to a very small extent; this is much less than one (is non-zero)

H2O is liquid at room temperature, whereas H2S, H2Se, and H2Te are all gases. Which of the following best explains why H2O is liquid at room temperature?

A: Hydrogen bonds form between H2O molecules
H2O is capable of forming intermolecular hydrogen bonds, but the rest are not

When aqueous solutions of the various anions and cations were mixed, precipitates formed because

A: The solubility product of a compound was exceeded
The amount of a substance that will DISSOLVE IN WATER is described by the Ksp. If the amount of the compound present is in excess of the Ksp, a precipitate would form to maintain the Ksp

Ba2+ is an ion that is very toxic to mammals when taken internally. Which of the following compounds, mixed in water, would be the safest if accidentally swallowed?

A: BaSO4, Ksp = 1.1*10^-10 (smallest amount given)
The lower Ksp, the lower the concentration of the cation and anion in an aqueous solution and the lower the solubility of the compound in water. If mixed with water and accidentally swallowed, the Ba salt

Which of the following changes in state function occurred during the dissolution shown in equation 1 (solid -> liquid):
I. H < 0
II. G > 0
III. S > 0

A: I and III
Because heat is liberated, the dissolution of solid NaOH is an exothermic process with enthalpy change H < 0. As NaOH dissolves, the system become more disordered, corresponding to a positive entropy change. The free energy is given as G=H-TS

Student E accounted for the equivalent weight found for succinic acid by analyzing its titration with NaOH(aq) and concluding that it is

A: Diprotic and requires twice the number of moles of NaOH expected for a monoprotic acid
Equivalent mass is the mass of an acid that yields one mole of hydrogen ions (= mass of base that reacts with one mole of hydrogen ions). Formula for succinic acid i

Aluminum belongs to what block of elements in the periodic table?

A: p
Aluminum is found in group 13 (3A) of the periodic table; it is a p-block element

In the reaction shown in equation 1, Al(OH)3 acts as what kind of acid or base?

A: Lewis acid
In the reaction the Al in Al(OH)3 accepts an electron pair from the oH- of NaOH and acting as a lewis acid

At which electrode is aluminum produced in a galvanic cell and an electrolytic cell?

A: At the cathode in both cells
Reduction of the Al3+ to form Al(s) occurs at the cathode both in a galvanic and an electrolytic cell

How many ppm is 1%

A: 10000
ppm stands for parts per million. Since 1$ is one part in 100 parts. The question becomes 1 is to 100 as * is to 100000 where x is unknown. Thus, x = 10000

The term "ideal gas" refers to a gas for which certain assumptions have been made. Which one of the following assumptions applies to an ideal gas?

A: Individual molecular volume and intermolecular forces are negligible
It's assumed that the molecules in an ideal gas have no volume and no interactions between the molecules

The frequency used in ultrasound imaging must be greater than

A: 20 kHz
Ultrasound is sound with a frequency above the human range of hearing (20Hz-20kHz); thus, anything greater than 20kHz will be ultrasound

Which of the following compounds is amphiprotic?

A: Sodium bicarbonate, NaHCO3
The prefix "amphi" means "both"; an amphiprotic species is one that can act as both an acid and a base. Sodium bicarbonate dissolves in aqueous solution to produce sodium ions and bicarbonate ions. While sodium ion is neither

Following the procedure of the experiment, how much total caffeine could you expect to extract?

A: 9.75g
Caffeine is largely nonpolar, so it will be more soluble in dichloromethane than in water. Therefore, it will dissolve more in the dichloromethane layer. Using the partition coefficient equations and the caffeine properties provided by the passag

In one trial of this experiment, significant impurities were detected in the extracted caffeine. Based on the results of the experiment, which of the following would be the expected melting point range for this extracted sample?

A: 195 - 220 celcius (I picked: 245-267)
A melting point range includes the temperature when the first crystal of a compound starts to melt and the temperature when the compound is entirely melted. For a pure compound, the melting point range is narrow (t

Which of the following statements correctly describe the methods used in the caffeine experiment?
I. The retention factor in a TLC procedure depends on the solvent system, temperature, and the adsorbent.
II. A polar compound will exhibit a smaller retenti

A: I, II, and III
I is true; TLC depends on the different affinity of a compound for the stationary vs. mobile phase. Therefore, depending on how polar the solvent and adsorbent are, a compound moves on a TLC plate at a certain rate. Temperature also affe

What is the normality of a 0.015M solution of phosphoric acid?

A: 0.045N
The chemical formula of phosphoric acid is H3PO4. NORMALITY refers to the number of moles of PROTONS per liter of solution ("molarity of proton").
Normality can be calculated by multiplying the molarity of the solution by the number of protons p

Which of the following ingredients would not aid a multivitamin in decreasing stomach acidity?
A.
Mg(OH)2
B.
Al(OH)3
C.
C2H5OH
D.
NaCN

Answer: C
A compound that would help decrease stomach acidity would be an antacid. Antacids are basic compounds that react with and neutralize stomach acids. We are looking for an option that is NOT a base (an acid or any non-base). Choice C is ethanol, w

What is the most likely formula for the ingredient shown on the label in Figure 1, called dibasic calcium phosphate?

A: CaHPO4
Phosphoric acid is H3PO4, and all three of its hydrogen atoms are acidic. As a result, there are three associated anions (PO43-, HPO42-, and H2PO4-), which are typically named phosphate, hydrogen phosphate, and dihydrogen phosphate, respectively

In comparison to the cohesive forces between water molecules of the protein solution droplet, how can the strength of interaction between water and oil molecules at an oil-water interface be characterized?

A: Weaker, because they are forces creased by induced polarity in nonpolar molecules
The Van der Waals forces existing between molecules of water and of oil are predominately of the induced dipole-dipole. Here, a small, temporary dipole is induced in mole

Which of the following acids is expected to generate the strongest hydrogen bonding?
A.
HI
B.
HF
C.
HCl
D.
HBr

A: HF
Hydrogen bond is an intermolecular force that occurs when H is bonded to a very electronegative elements like F, O, or N.

A certain type of tissue is sensitive to radiation with the damage the tissue receives being directly proportional to the charge on the irradiating particle. Which of the following radiation types will cause the least damage?

A: Gamma
Gamma particles have no charge as they are simply high-energy photons. Since the question says that the damage is proportional to charge, a particle with no charge would cause the least damage
- Alpha particles have a +2 charge and would be the m

A researcher carries out a column chromatography at physiological pH, using a stationary medium with a net positive charge. If a solution containing the following oligopeptides is poured into the column, which oligopeptide will most likely be found in the

A: KRVV
If the stationary phase has a net positive charge, then oligopeptides with negative charges will be attracted to the stationary phase and will move more slowly through the column. KRVV has a charge of +2; it would not bind the stationary phase and

A patient presents in the emergency department having ingested a large quantity of tolbutamide. Intravenous administration which of the following compounds is most likely to increase the rate of urinary excretion of the drug?
A.
KCl
B.
NaHCO3
C.
NH4ClO4
D

A: NAHCO3
To increase the percentage of drug excreted in the urine, we must decrease the fraction of tolbutamide capable of reabsorption, or diffusion out of the lumen of the nephron. Passage indicates that for weakly acidic drugs, the uncharged state is

Ten moles of the monoprotic, weakly acidic medication aspirin were added to water to make one liter of solution. If the pH of the resulting solution was 5.9, what is the approximate Kb for the non-diffusible form of aspirin?

A: 0.1
Since we are given pH in the question stem, we will not be able to find Kb immediately. Instead, we need to calculate Ka and solve for Kb from that value. The Ka for the dissociation of a generic acid HA can be written as Ka = [H+][A-]/[HA], where

According to the description in the passage, Earth is:

A: closed system
Earth satisfies both conditions of a closed system. There IS energy exchange but not mass exchange with surroundings.
- An isolated system exchanges NEITHER energy nor mass with its surroundings.

What is the primary process responsible for the loss of latent heat and entropy from the ocean at the air-sea interface

A: Evaporation
A negative latent heat implies that the phase change that is occurring is consuming energy. Therefore, the phase change that is occurring is melting, evaporation or sublimation. The fact that this process is occurring at the air sea interfa

Assume the hydrolysis of ATP proceeds with G= -30kJ/mol:
ATP + H2O -> ADP + Pi
Which expression gives the ratio of ADP to ATP at equilibrium if the [Pi]=1M? (RT=2.5KJ/mol)

A: e^12
The free energy of the reaction G is related to the equilibrium constant Keq = [ADP][[Pi]/[ATP] as G= -RTln(Keq). Thus, by plugging in, [ADP/ATP] = e^12

What is the electronic configuration of the Co(II) center found in vitamin B12?

A: [Ar]3d^7 (I picked: [Ar]4s^2 3d^7)
CO(II) is a diction formed from the atomic element by the loss of two 4s electrons (outer shell). Thus, only 7 3d electrons remain in the valence shell.

In a certain kinetic experiment, the enzymatically catalyzed hydrolysis of ATP proceeds at a constant rate of 2?Ms^-1. If the volume of solution is 1mL, what is the total number of ATP molecules that hydrolyzed after 1 min?

A: 1.2*10^-7 mol
The total number of molecules that were hydrolyzed can be calculated by multiplying the rate in ?Ms^-1 by the time (in second) and volume of the solution (in L): 2
10^-6 mol
L^-1
s^-1
60s
1
* 10^-3 L = 1.2 * 10^-7 mol

Which cations is most likely to be found in place of Fe(II) in the square planar binding domain of hemoglobin?

A: Co2+ (Picked Mg2+)
Co2+ is closely related to Fe2+ as a transition metal and support a square planar coordination environment

The ATP-dependent phosphorylation of a protein target is catalyzed by which class of enzyme?

A: Transferase
Kinases catalyze the transfer phosphate groups from ATP to target proteins and are classified as transferases.

What was the most likely purpose of adding bovine serum albumin to the kinetics experiments in the passage? Bovine serum albumin:

A: Prevents the esterase from adhering to the walls of the vessel
Passage states that albumin is a protein that mobilizes proteins and lipids in serum. In the context of a kinetics experiment, it's logical to assume that albumin is added to maintain homog

Which experimental techniques was most likely used by the students to determine the rate of reaction?

A: Monitor the increase in absorbance of the solution at 360nm
The experiment describes that the substrate was chosen based n the fact that it produced a yellow colored product (compound 2). The complementary color to yellow is purple, which is ~360nm.

The unknown compound was probably a

A: Weak acid (Picked "strong acid")
The passage states: "The compound completely dissolve in water and weakly conducted electricity. The hydrogen ion concentration of the unknown aqueous solution was 1*10^-5M"; picked my answer because "completely dissolv

Two additional compounds were studied: NO2(OH) dissolved in water and produced an acidic solution, and Ni(OH)2 dissolved only in an acidic solution. What type of compounds were these?

A: NO2(OH) was an oxyacid and Ni(OH)2 was a base
The first substance is nitric acid (HNO3). Since this dissolves to generate an acidic solution, the bond between O and H in NO2OH breaks when the substance dissolves, making it an oxyacid. Ni(OH)2 is insolu

What is the concentration of Cl- ions in a 0.1M solution of calcium chloride?

A: 0.2M
The formula for calcium chloride is CaCl2 and it produces twice as many Cl- ions as Ca2+ ions in solution when it dissolves

Suppose that at the end of reaction 1 the level of the aqueous solution were 26cm higher inside the buret then outside. Compared to ambient pressure, the pressure of the gas inside the buret would be

A: Lower
Because the level of the liquid inside is higher than outside which results from the fact that the air pressure outside is higher than the pressure inside. Pressure builds on the inside by raising the liquid level. When the sum of the inside air

The principal quantum number is a measure of which of the following?

A: Approximate radial size of an electron cloud
The principal quantum number n is most closely associated with the potential energy of the electron. Since potential energy is proportional to the square of the distance of two oppositely charged particles b

What is the net charge of both pantothenate and phosphopantothenate in aqueous solution at pH 7?

A: -1 for pantothenate and -3 for phosphopantothenate
In water at pH 7, the carboxylic acid of pantothenate will lost a hydrogen ion to become a carboxylate (-1) for a net charge of -1 on pantothenate. The phosphate groups of phosphopantothenate will lost

O2 dissociates more readily from Hb in an acidic environment. This dissociation will therefore occur most readily when the PCO2 is

A: High, because the equation (CO2+H2O -> H2CO3 -> H+ + HCO3-) will proceed to the right.
(I picked "High, because the equation will proceed to the left" because CO2 is acidic)
Analysis of equation 1 leads to the conclusion that increasing concentration o

While solving a chemistry problem, a student uses the equation ?G = -nFE to determine that the ?G = -178 kJ/mol. Which of the following must be true about this reaction?
I. The reaction is spontaneous.
II. The reaction is exothermic.
III. The reaction inc

A: I
The change in Gibbs free energy determines the spontaneity of the reaction. A negative G indicates a spontaneous reaction.
Whether a reaction is endo or exothermic is determined by enthalpy (H) not G.
Whether the entropy of reaction increases or decr

Which of the following phosphate ions is amphiprotic?
A. PO43-
B. HPO42-
C. P2O74-
D. H3PO4

Answer: B
An amphiprotic species is one that can act both as an acid and a base. Hydrogen phosphate HPO42- can dissociate a hydrogen ion to form PO43- and therefore act as an acid. It can also accept a hydrogen ion from water to form H2PO4- and act as a b

The crystal precipitate formed in collected effluent was composed principally of calcium carbonate, with strontium carbonate inclusions. The large majority of the crystal units did NOT include strontium because the:

A: Effluent strontium ion concentration was much smaller than the effluent calcium ion concentration (I picked: "solubility constant of strontium carbonate is less than that of calcium carbonate")
Precipitate forms when the ion product, Q, for a compound

The addition of which of the following compounds to water would reduce the solubility of ferrous (II) hydroxide?
A. Ammonia
B. Ethanol
C. Acetic acid
D. Trichloroethane

A: Ammonia
This is a common ion effect question. The presence of a common ion in the solution prior to dissolving will cause the reaction to reach equilibrium faster (i.e. at a lower concentration of reactants). Because ferrous (II) hydroxide produces hyd

Given the role of the reaction in cellular respiration, what is the most likely E� value for the reduction of oxygen to water?

A: 0.82V
Positive E� values correspond to compounds that are easily reduced. As the final electron acceptor in the ETC, oxygen must be prone to reduction than any of the other electron carriers. Positive E� means that the associated reaction is spontaneou

Besides directly killing bacteria, how does pasteurization with hot water treat IPB populations?

A: By decreasing the solubility of oxygen, preventing further bacterial growth
Oxygen, like all gases, is more soluble in cold water than warm water. Thus, the process of heating water (pasteurization) would lower solubility of oxygen and reduce the amoun

In locations with very low dissolved O2 concentrations in drinking water, the observed Ksp of ferrous (II) hydroxide will be

A: the same
Equilibrium constants, including Ksp, are not affected by concentration. These constants are ONLY altered by changing temperature

What is the molar solubility of ferrous (II) hydroxide in water at 25�C?

A: 2.1*10^-5
The passage states that the Ksp of ferrous (II) hydroxide is 3.2 x 10-14. When Ksp is known, we can determine molar solubility from the dissociation reaction.
Fe(OH)2 (aq) + H2O (l) ? Fe2+(aq) + 2 OH- (aq)
Note that Fe(OH)2 dissociates into t

In a gas experiment, a student wished to measure the deviation of non-ideal xenon gas at various temperatures and pressures. For one mole of non-ideal xenon gas at a pressure of 1000 atm and a temperature of 100K, what is the most likely value for the qua

A: 3
For one mole of an ideal gas (n=1) the quantity PV/RT equals 1 for all pressures. Deviations from the ideal gas law occur at high pressures and low temperatures. Here, the main assumption that is broken is that gas particles have no volume. Recall th

Absorption of radiation corresponding to what portion of the electromagnetic spectrum is most likely to excite Aequorea fluorophore, a green fluorescent protein used in biological experiments?

A: Ultraviolet
Fluorescence is the emission of a lower energy photon from a fluorophore excited by the prior absorption of a higher-energy photon. Thus, the Aequorea fluorophore must be excited by the absorption of a photon of higher energy (and frequency

he reduction potential for Zn2+ is -0.66 V. Combined with the data in Table 1, which of the following most likely represents the standard reduction potentials for the half-reactions shown below?
Cu2+ (1.0 M aq) + 2 e- + Cu (s) E1� =
Ni2+ (1.0 M aq) + 2 e-

A: E1 = 0.34V, E2 = -0.23V, E3 = -2.18V
For a galvanic cell, the total cell potential is the sum of the reduction potential of the cathode and the oxidation potential of the anode. Since we're looking for reduction potentials, and since reduction occurs a

For the student cell that produced the highest positive voltage, which of the following changes would produce an even higher positive voltage?

A: Decreasing the concentration of the Mg2+solution and increasing the concentration of the Cu2+ solution
The overall net ionic redox reaction for this cell is:
Mg (s) + Cu2+ (aq) ? Mg2+ (aq) + Cu (s)
The Nernst equation, E = E� - 0.059/n log Q, can be us

An artificial vesicle containing a 1 M glucose solution is composed of a phospholipid bilayer lacking any protein components other than aquaporin channels. Assuming an ideal solution, what is the ratio of the osmotic pressure measured immediately after im

A: 0.67
The situation described in the question is analogous to a semipermeable membrane. Water is able to pass through aquaporin channels present in the liposome, but large uncharged particles (glucose) and ions (K+ and Cl -) are impermeable and will rem

During the reduction of a mole of oxygen to water shown in Figure 1, how much charge is transferred?

A: 4*10^5 C
First, we need to balance the reaction:
O2 (g) + 4 H+ ? 2 H2O (l)
This reaction is now balanced in terms of atoms, but as a redox reaction, it must also be balanced with regard to charge. We currently have a +4 charge on the left and a 0 charg

Which of the following is (are) present in a mixture of NH3 and BF3?
I. FLP
II. Br�nsted-Lowry acid
III. Br�nsted-Lowry base

A: III
BL bases are species that accept protons, and BL acids are species that donate protons. NH3 has a lone pair on the N that accepts protons to form NH4+, or ammonium. Thus, it is a BL base and RN III is correct.
I: The passage states that FLP are mix

Turbulent flow in humans is a major risk factor for atherosclerosis, the buildup of plaque on arterial endothelium. Ignoring any potential effects of turbulence, what effect would atherosclerosis have on blood flow?

A: Narrowing of the artery causes the velocity to increase and the hydrostatic pressure to decrease
The buildup of plaque in the lumen of the vessel would cause a narrowing of the vessel. The question then implies that we must consider the Venturi effect,

Under what set of conditions would an air embolism be MOST likely to form in blood?

A: 42�C and PO2 = 120 mmHg
According to the first and second paragraphs, an air embolism is caused when a bubble of air is formed in the blood and blocks a vessel. If a gas is insoluble in a fluid, it can escape as a bubble (think of warm soda going flat)

In which of the following aqueous carbohydrate solutions would a given vesicle have the greatest buoyancy?
A. 0.15 M sucrose
B. 0.15 M glucose
C. 0.20 M fructose
D. 0.25 M galactose

Answer: A
Buoyancy is the force that results from the displacement of fluid when an object is submerged. The magnitude of the buoyant force is equal to the weight of the fluid displaced. Therefore, the greater the density of the solution, the larger the b

If the average bone mineral density is 3.88 g/cm3, which of the following is a reasonable estimation of the density of the average human body?
A. 0.001 g/cm3
B. 1 g/cm3
C. 3.88 g/cm3
D. 4.88 g/cm3

Answer: B
Bones are the most dense part of the human body so the overall body should have a density lower than 3.88g/cm^3. We can also consider the fact that humans typically float right at the surface of water, implying that the density of the human body

Subsequent solvation studies employing other haloalcohols revealed the strongest interaction between Trp19 in monomeric melittin and the hydrophobic component of what solvent molecule?
A. 2,2-difluoroethanol
B. 2-fluoroethanol
C. 2,2-dichloroethanol
D. 2-

Answer: D
The four molecules differ in the number and strength of electron-withdrawing halogen atoms present. Specifically, as the number and electronegativity of the halogens present decreases, the polarity of the molecule will decrease as well, increasi

Pulmonologists use BCG to measure respiratory rate during exercise by having patients exhale into an aqueous solution containing the indicator. Which of the following would be observed in the final solution?

A: The formation of carbonic acid and the solution turning yellow
The patient's exhalation will cause CO2 from his breath to be absorbed into the solution. As we've seen in the blood, when carbon dioxide mixes with water, it forms carbonic acid. CO2 + H2O

Tissue engineers have been developing a synthetic mineral apatite to use in prosthetics that is comprised of repeating molybdenum hexacarbonyl [Mo(CO)6] subunits. This bonding is likely to involve which of the following orbitals?
A. sp3
B. sp3d2
C. d2sp3

Answer: C
Here, the central molybdenum atom is bound to six substituents. In such a configuration, the molecule takes the shape of an octahedron. The number of substituents (bonding regions) around the atom is equal to the number of orbitals that can hybr

In an isolated system, entropy is maximized when:
I. the system is at equilibrium.
II. the system is far from equilibrium.
III. the system is unable to perform work.

A: I and III
Recall at equilibrium, with no free energy change, the system is unable to perform work. At equilibrium, there are no energy gradients within the isolated system, so energy is maximally dispersed, resulting in maximal entropy
- A system far f

Hydrogen bonds vary in strength depending upon the donor and acceptor atoms. Which of the following hydrogen bonds has the lowest bond dissociation enthalpy? (A dashed line indicates the hydrogen bond in question.)
A. F-H - - - :O
B. N-H - - - :O
C. O-H -

Answer: D
This question is asking for the weakest bond. Since the acceptor atom is oxygen in all four choices, we need only consider the effect of the electronegativity of the donor atom on the strength of the bond. Fluorine is the most electronegative at

A student sought to remove the H2O and CO2 gas emitted by the animals in separate chambers instead of using silica gel and soda lime. 224 mL of each gas was collected at a pressure of 1 atm. What will be the expected ratio of the mass of CO2 to that of H2

A: 2:1
In this, as the two chambers are connected, the pressure and volume for each gas must change while the temperature is held constant. For both gases, the new volume is the total volume of both chambers. Given that the volumes of the two gases are eq

A student places a vial of gas at the bottom of a graduated cylinder. A liquid sample is suspended in a chamber at the top of the cylinder. The vial is broken and the gas is allowed to diffuse throughout the cylinder. When the two compounds mix, a black p

A: Neon
Rate of effusion is inversely related to the square root of molecular weight: rate ? 1/? (MW). Thus, the smaller the molecular weight, the higher the rate of effusion. Examining the periodic table, we can see that neon has the lowest molecular wei

#7. Which of the following has the smallest atomic/ionic radius?
A. K+
B. Ca2+
C. Ar
D. Cl-

Answer: B
All four answer choices are isoelectronic: they have the exact same configuration and number of electrons. The main difference between them is the number of protons in their nucleic. Protons, which are positively charged, attract electrons. Calc

What are the units for k in the following rate law: rate = k[A]2[B]? Note that the concentration unit is mol/L.

A: L2mol-2s-1
We can see that the reaction is third order overall, and reaction rates are measured in M/s, where M = mol/L. Thus, we can set up our equation:
M/s = k (mol/L)3 = k (mol3/L3)
k = (M/s) (L3/mol3) = (mol/L�s) (L3/mol3)
k = L2/s�mol2 = L2mol-2s

Consider the chemical reaction NH4+(aq) + NO3- (aq) ? N2(g) + 2H2O(l).
Trial [NH4+] [NO3-] [Reaction Rate]
1 0.010M 0.02M 0.20M/s
2 0.015M 0.02M 0.30M/s
3 0.010M 0.01M 0.05M/s

A: rate = k[NH4+][NO3-]2
With rate law problems, we should first identify two trials where only one of the reactants changes concentration. Between trials 1 and 3, we can see that the concentration of nitrate doubles while the rate quadruples. This means

Before coordination to protoporphyrin, what is the ground state electron configuration of Co2+?

A: [Ar]3d^7
During the ionization of transition metals, electrons from 4s subshell orbitals are generally removed before those from 3d subshell orbitals. This is because electrons of 4s subshell orbitals are higher energy than those in 3d subshell orbital

Under anaerobic conditions, bacteria can sometimes derive energy from the oxidation of sulfur-containing species. Which of the following can NOT be oxidized by anaerobic bacteria?

A: SO42- (aq)
Of the answer choices, the oxidation number for sulfur would need to be in a reduced form. The highest oxidation state for sulfur is +6, corresponding to the loss of all of its valence electrons. The oxidation number for sulfur (x) in sulfat

Which of the following is most likely to undergo positive beta decay?
A. 14C
B. 13C
C. 17O
D. 22Na

Answer: D
Positive beta decay, known as positron emission, occurs when the proton-to-neutron ratio is too high. Of the options given, 22Na has the highest ratio as it has 11 protons and 11 neutrons (1:1)

The half-life of 18F is 110 minutes. If 5 grams of FDG remain after 5 hours and 30 minutes, how much energy was emitted from the patient's body in the form of gamma rays from radioactive decay of the FDG?

A: 1.19 x 1026 keV
This question requires us to determine how many half-lives have occurred after 5.5 hours. 5.5 hr x (60 min/1 hr) = 330 minutes, or 3 half-lives. Working backwards from the final amount of 5 g we see that we must have started with 40 g o