The Universal Solvent
Water
Solvent
a substance which can be used to dissolve another substance. Generally the larger amount
Solute
a substance which is dissolved by another substance. Generally the smaller amount.
Solution
a mixture of a solute and solvent. The solute is aqueous (aq) when in water. A solution is a homogeneous mixture
Like dissolves like
Water has a dipole, so it is good at dissolving charged or polar molecules. Water is not that good at dissolving some nonpolar molecules (Carbon and Hydrogen have a small electronegativity difference).
Homogeneous Mixture
also called a solution. A homogenous mixture is a solution that has a uniform consistency (composition) throughout, for example, a salt solution after dissolving and mixing it thoroughly. Not only that but also the individual components cannot be identifi
Heterogeneous Mixture
A heterogeneous mixture does not have uniform composition like homogeneous mixture where the individual components can be identified, for example, a mixture of sand and salt. The components do not have a uniform composition. For example, a mixture of oil
Solutions: a Molecular view
water dissolves ionic compounds by surrounding the ions with the charges of the dipole. So NaCl (aq) is really Na (aq) and Cl (aq). Solutions are homogeneous mixtures.
Electrolytes
electrolytes are ions produced by the dissolving of an ionic compound in water. Strong electrolytes exist only as ions in solution (fully dissociate). Weak electrolytes exist only partly as ions in solution (partially dissociate).
Ionic compound
a compound of positive and negative ions held together by ionic bonds.
Strong electrolytes
ionic compounds which fully dissociate into ions in water
weak electrolytes
ionic compounds which only partially dissociate into ions in water.
Nonelelectrolytes
compounds which do not dissociate into ions in water, but dissolve and remain as molecules (covalent compounds - sugar, ethanol)
Conduction of Electricity
electricity is the flow of electrons through a substance. Water by itself does not conduct electricity. For water to conduct electricity, ions must be present in solution - the more ions, the better the solution can conduct electricity.
which of the following may describe a base?
when dissolved in water, may donate a hydroxide ion. When dissolved in water, may accept a hydrogen ion. When dissolved in water, has a pH greater than 7.
A mixture of large particles in water which settle out would be described as a
suspension
catalyst
a substance that increases the rate of reaction by lowering the activation energy.
How does a catalyst speed up the rate of reaction
by decreasing the activation energy of a reaction
what is the name of the solution formed when HClO2 is dissolved in water?
Chlorous acid
which of the following statements are true regarding strong electrolytes?
strong electrolytes form a solution in water. strong electrolytes are made up of ions. Hydrochloric acid is a strong electrolyte.
In a solution, the solvent
can be solid, liquid or gas
Hydrogen gas and Chlorine gas are in a closed, rigid container, and react to form Hydrogen Chloride in a combination reaction. This reaction is exothermic, so warms the container and its contents. Which of the following statements is true?
the pressure in the container will increase
When some of the sugar added to iced tea remains undissolved at the bottom of the glass, the solution is
saturated
H2PO4- in solution may act as an acid. What ion or molecule would be the conjugate base?
HPO4^2-
KBr is a strong electrolyte. When KBr dissolves in water
the K+ ions are attracted to the partially negative Oxygen atoms of the water molecule.
When one mole of each of the following is added to one mole of water, which will be the best conductor of electricity?
Potassium Carbonate
Assuming an exothermic reaction is reversible, how would heating likely affect the reaction?
the equilibrium would shift toward reactants
A solution is made by mixing 750mL of ethanol, 292mL of water, 1 gram of sodium chloride and 10 grams of sodium bicarbonate. What is the solvent in this mixture?
ethanol
A solution of silver nitrate is added to a solution of calcium chloride, and a white precipitate is observed. What is the likely identity of the precipitate?
silver chloride
In water, a substance that ionizes completely in solution is called a
strong electrolyte
which of the following will increase the solubility of a gas in water?
increasing the pressure of the solution and cooling the solution.
which of the could carry out a neutralization reaction?
HBr and LiOH
For the reaction shown her, which of the following statements is true?
N2 + 3H2 -> 2NH3 + 22.1 kcal
products have less potential energy than the reactants
Which of the following is NOT true about a reversible chemical reaction at equilibrium?
the exchange of molecules between reactants and products stops
a sample of zinc(II) hydroxide is dropped into an aqueous solution of hydrogen nitrate (nitric acid), resulting in a neutralization reaction. Approximately how many grams of zinc hydroxide was present in the sample if 0.375 moles of water are produced?
20 grams
Old dynamite may explode if dropped a short distance or shaken. Which of the following would be the best description of the energy involved in this reaction?
it has a small activation energy and a large heat of reaction
In the process known as osmosis, ________ moves through a semipermeable membrane into an area of _______ concentration.
solvent, higher solute
Nitrous oxide is used in some dental offices as a mixture of 67% NO2 and 33% O2. You visit the dentist and see that he has a tank of this, and the pressure gauge reads 5.6 atm. What is the pressure of NO2 gas in this container?
3.8 atm
The percent concentration by mass refers to
mass of solute / mass of solution
To make a solution, 203 grams of acetone and 23 grams of zinc(II) chloride are dissolved in 520 grams of water. Which number is closes to the percent concentration by mass of zinc(II) chloride in solution?
3%
To make a solution, 39 mL of water is added to ethanol for a total volume of solution of 152 mL. Which number is closest to the percent concentration by volume of water in the solution?
25%
A(n) _______ is a type of colloid in which a liquid is dispersed in another liquid or a solid
emulsion
Colloids
mixtures having particles that are moderately large. Colloids pass through filters bur cannot pass through semipermeable membranes
Ammonium hydroxide is a weak base because
it dissociates into ions only partially in water.
Classification of Matter is based on Composition
When we talk about matter, usually we talk about a substance which posses distinct properties and has a definite composition. For example sugar (sucrose), table salt (sodium chloride), water, gasoline, etc. All substances do not have the same composition
Element
a pure substance containing only one type of matter, which cannot be broken down by chemical methods. Ex. Silver metal, Oxygen gas, Iron.
Compound
a pure substance consisting of two or more elements, with a definite composition, that can be broken down into simpler substances only by chemical methods. A compound is the substance formed by the chemical union of two or more elements in a definite rati
Pure substances
Matter composed of elements or compounds that has a definite composition.
Conductivity of Solutions
An electric current is a flow of electrical charge. When a metal conducts electricity, the charge is carried by electrons moving through the metal. Electrons are subatomic particles with a negative electrical charge. When a solution conducts electricity,
Equivalents
Body fluids contain a mixture of several electrolytes, such as Na+, Cl-, K+, and Ca2+. We measure each individual ion in terms of an EQUIVALENT (Eq), which is the amount of that ion equal to one mole of positive or negative electrical charge. For example,
Saturated solution
a solution containing the maximum amount of solute that can dissolve at a given temperature. Any additional solute will remain undissolved in the container.
Super saturated solution
when a saturated solution is carefully cooled, it becomes a supersaturated solution because it contains more solute than the solubility allows, although it is still completely liquid. Such a solution is unstable, and if the solution is agitated or if a so
Effect of Temperature on Solubility
the solubility of most solids becomes greater as temperatures increase, which means that solutions usually can contain more dissolved solute at higher temps.
unsaturated solution
a solution that contains less solute than can be dissolved.
Suspensions
a mixture in which the solute particles are large enough and heavy enough to settle out and be retained by both filter and semipermeable membranes
aerosol
a colloidal dispersion of solid or liquid particles in gas. A substance, such as a paint, polish, or insecticide, dispensed from a small metal container by a propellant under pressure
foam
a colloid consisting of a gas suspended in a liquid
emulsions
An emulsion is a colloid of two or more immiscible liquids where one liquid contains a dispersion of the other liquids. Immiscible is the property where two substances are not capable of combining to form a homogeneous mixture.
Examples:
Oil and water are
osmosis
a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one, thus equalizing the concentrations on each side of the membrane.
isotonic solutions
a solution that has the same osmotic pressure as that of the red blood cells of the body.
hypotonic solutions
a solution that has a lower osmotic pressure (lower concentration of solutes) than the red blood cells of the body.
hypertonic solutions
a solution that has a higher osmotic pressure (has more solutes) than the red blood cells of the body.
Law of Conservation of Energy
Law which states energy cannot be created or destroyed, but may be changed from one form to another.
Exothermic reaction
term used to describe a reaction or process that releases energy in the form of heat. Sometimes the term is applied to processes that release other forms of energy, such as electrical energy, sound, or light.
Example: combustion of wood
Endothermic reaction
An endothermic reaction is any chemical reaction that absorbs heat from its environment. Here's a list of examples of endothermic reactions. You can use these when asked to cite an example or to get ideas to set up a demonstration of an endothermic reacti
Activation energy
The least amount of energy needed for a chemical reaction to take place.
heat of reaction
the heat absorbed or released when a reaction takes place
catalysts in a chemical reaction
another way to speed up a reaction is to lower the activation energy. We saw that the activation energy is the minimum energy needed to break apart the bonds of the reacting molecules. If a collision provides less energy than the activation energy, the bo
Reversible reactions
a reaction in which a forward reaction occurs from reactants to products and a reverse reaction occurs from products back to reactants.
Equilibrium
at equilibrium the rate of the forward reaction is equal to the rate of the reverse reaction. No further changes occur in the concentrations of the reactants or products; the forward and reverse reactions continue at equal rates.
Factors that affect the rate of reaction
temperature, concentrations of reactants, catalysts
three conditions required for a reaction to occur
1. collision - the reactants must collide
2. orientation - the reacts must align properly to break and form bonds.
3. energy - the collision must provide the energy of activation
Le Chatelier's Principle
when a system at equilibrium is disturbed, the system will shift in the direction that will reduce that stress.
Arrhenius
acids form H+ (proton or hydrogen ion) when dissolved in water, bases form OH- (hydroxide ion) when dissolved in water
Bronsted-Lowry
Acids donate a proton (H+) to another substance, bases accept a proton.
acids and bases
when mixed, carry out neutralization reactions to form water and a salt (water=hydrogen hydroxide)
characteristics of an acid
pH below 7, positively charged ion, donate a proton, sour, neutralize bases
characteristics of a base
pH above 7, negatively charged ion, receive a proton, bitter/chalky, soapy, neutralizes acids
strong acids vs weak acids
strong acids fully dissociate in water. The H3O/Hydronium ion is the strongest acid that can exist in aqueous solution. Water acts as a Bronsted-Lowry base, by accepting a proton from the acid in solution.
Conjugate Acid-Base Pairs
Strong Acids dissociate to form weak base (reluctant H+ acceptor) and a proton. Strong bases dissociate to form a weak acid (reluctant OH- acceptor) and a hydroxide ion
Conjugate Acid-Base pairs are inversely related. The stronger a conjugate acid, the we
Common reactions of Acids
Acids react with certain metals to produce a salt and hydrogen gas (H2). Metals that react with acids include potassium, sodium, calcium, magnesium, aluminum, zinc, iron, and tin. In reactions that are single replacement reactions, the metal ion replaces
balancing neutralization equations
in a typical neutralization reaction, one H+ always combines with one OH-. Therefore, a neutralization equation may need coefficients to balance the H+ from the acid with the OH- from the base.
Strong bases
Strong bases dissociate 100% into the cation and OH- (hydroxide ion). The hydroxides of the Group I and Group II metals usually are considered to be strong bases.
�LiOH - lithium hydroxide
�NaOH - sodium hydroxide
�KOH - potassium hydroxide
�RbOH - rubidi
Strong Acids
Strong acids completely dissociate in water, forming H+ and an anion. There are six strong acids. The others are considered to be weak acids. You should commit the strong acids to memory:
�HCl - hydrochloric acid
�HNO3 - nitric acid
�H2SO4 - sulfuric acid