KHP is considered a
Primary standard because the solid compound is stable in air and can be massed accurately
What is true about KHP?
A. It is also known as potassium hydrogen phthalate
B. It is also known as potassium biphthalate
C. It is also known as potassium acid phthalate
It is noted in the experimental procedure that solid sodium hydroxide pellets are deliquescent. This refers to
the ability of NaOH to rapidly absorb water from the atmosphere
A. Clear Colorless
B. Dark Pink
C. Light Pink
A 1. Before endpoint
C 2. At the endpoint
B 3. Overshot the endpoint
The color at the endpoint of the titration (check all that apply)
Should be faint, Should persist for a minimum of 30 seconds
When using titration to determine the concentration of a solution
The concentration of one of the two solutions used in the titration must be known
A solution is properly mixed by
closing the container and shaking a minimum of 20 times.
If air bubbles are observed in the tip of the buret
A small amount of titrant should be drained from the buret through the buret tip
Leaving spilled material on a balance pan can (check all that apply)
corrode the metal surface of the balance pan
C. pose hazards to other students
D. cause inaccurate readings
In the Acid Base Titration procedure a solution of _____ is prepared.
Sodium hydroxide
It is noted in the experimental procedure that solid sodium hydroxide pellets are deliquescent. This refers to
the ability of NaOH to rapidly absorb water from the atmosphere.
The indicator used in the titration will be (of the acid base titration week is
phenolphthalein
An Erlenmeyer flask is often used for titrations because
It is designed to reduce the risk of losing solution due to splashing.
In a titration
One solution is added dropwise to a predetermined quantity of another substance until an end-point is reached
A solution is properly mixed by
closing the container and shaking a minimum of 20 times.
Which of the following could be a reading from a nearly full 50 mL buret with markings every tenth milliter
B. 0.10 mL
When titrating, the solution should
Be mixed throughout the addition of titrant
The balances in the UD chemistry laboratories read masses to four decimal places. When recording the mass of sample on a data sheet
C. all numbers shown should be recorded
The point in a titration at which one reactant has been exactly consumed by addition of the other reactant is known as the
Equivalence point
Phenolphthalein is used in the Acid Base Titration II procedure
indicator
In the Acid Base Titration II procedure the sodium hydroxide solution used
Was prepared in lab the previous week
Which of the following is an Erlenmeyer flask
If a solution is prepared by diluting a more concentrated solution, insufficient mixing of the prepared solution will result in
the concentration of solution near the top of the container likely being less than the concentration of solution in the bottom.
When rinsing a buret with DI water or titrant
The buret should be held horizontally and rolled
In the Acid Base Titration II procedure the experimental task is to
Determine the molar mass of an unknown acid
One mole of a monoprotic acid requires ___ moles of sodium hydroxide to reach the equivalence point.
One
A buret should be filled
to below the 0.00 mL mark
The safety policies of the University of Dayton General chemistry program are
Based on the guidelines of the American Chemical Society.
One mole of a triprotic acid requires ___ moles of sodium hydroxide to reach the equivalence point.
Three
When titrating to an endpoint
Titrant can be added rather quickly at the start and then should be added dropwise near the endpoint
When rinsing a buret with DI water or titrant approximately ___ mL of water or titrant should be used
D. 5 mL
The safety shower is located
Next to the emergency exit near the back of lab.
Titration of the unknown acid with NaOH should be repeated a minimum of ____ times.
4
Standardization
the analytical determination of molarity of solution. For NaOh - titration is necessary because it is not possible to directly prepare a known molarity solution of NaOH with accuracy.
Primary Standard
a substance of very high purity wich is stable in air. Because it remains pure it is possible to mass a sample of the substance with a high degree of accuracy.
Volumetric Flask
...
Buret
Magnetic stirrer
...
titration
completed in which a buret is used to dispense measure increments of solution into a second solution or an unknown acid.
Objective: to detect when the reactants are present in stoichiometric equivalent amounts
Monoprotic Acid
HA + NaOH> NaA + H2O
Diprotic Acid
H2A + 2NaOH > Na2A + 2H2O
Indicator
used to signal the equivalence point.
Phenolphthalein
Indicator which is clear in acidic solution and pink in basic solution.
End point
actual point at which the indicator changes color.
Deliquescent
having the ability to rapidly absorb water from the atmosphere. Ex. NaOH
Calculating molarity of NaOH
(mass of KHP,g) (1/Molar mass KHP) = mol KHP
(mol KHP)(1 mol NaOH/1 mol KHP) = mole NaOH
mol NaOH/volume NaOH L = molarity
Molar Mass of the Unknown Acid
(volume NaOH L)(M of NaOH) = mole NaOH
mono, diprotic, triprotic:
diprotic
mole naoh x 1/2 = moles of acid mass/ moles= molar mass
Precision
repeatability, a measure of how close a series of measurements are to one another, reprodicibility
Accuracy
a measure of how close a measurement comes to the actual or true value of whatever is measured
Impact of NaOH in a plastic bottle in ait
concentration would increase because NaOH would evaporate with water. So there would be a lower amount of solution per liter of water
NaOH is not restandardized after some water evaporated - quantity
Would impact the quantity: the amount of solution necessary to reach the endpoint would decrease due to the increased concentration of the solution.
NaOH is not restandardized after some water evaporated - atomic molar mass
Calculated molar mass would increase because there would be fewer moles to react with the unstandardized NaOH. With less there would be a higher gram to mol ratio.
Hess's Law
Reaction enthalpy is a state function, the enthalpy changes of a series of reactions can be combined to determine the enthalpy change of a reaction that is the sum of the components of the series.
Heat Transferred
(Heat capacity of solution)(change in T)
Heat capacity of solution
(mass of solution)(specific heat of solution)
specific heat of water 4.184 J/gC
Calculation of enthalpy
heat transferred/moles of reactant reacted
According to the Significant Figures Guide in the front of the manual, if a graduated cylinder has markings every 1 mL, how many decimal places should be recorded in the volume?
1
According to the Significant Figures Guide in the front of the manual, how would the volume of a 100 mL volumetric flask be recorded using proper number of significant figures?
100.00 mL
Volumetric Flask
Graduated Cylinder
Buret
Which of the following observations are quantitative? (Select all that apply)
A. Gas bubbles formed during the reaction
B. The substance is solid at room temperature
C. The mass of the solid is 1.3476 g
D. The volume liquid used is 24.56 mL
E. The solutio
C. The mass of the solid is 1.3476 g
D. The volume liquid used is 24.56 mL
The volume of a liquid contained in a graduated cylinder is determined by
C. Reading the bottom of the meniscus at eye level
When drawing liquid into a pipet
B. Draw liquid up just slightly past the graduation mark on the pipet