CEM 142 CORE EXAM 2026 TEST QUESTIONS AND
SOLUTIONS SCORED A+
✔✔Buffer:
Contains boh a weak acid and its conjugate base.
The acid part (HA) will react with any added __________ base.
*HA+B- --> HB + A- (where B- is a strong base, and A- is the weaker conjugate base of
HA)
The base part (A-) will react with and added _________ acid.
*A-+HX --> HA+X- (where HX is a strong acid, and HA is the weaker conjugate acid of
A-). - ✔✔-Strong base.
-Strong acid.
✔✔In effect we are exchanging a strong acid for a week acid- or a strong base for a
weak base- and weak acids or bases ______ _________ affect the pH as much. - ✔✔-
DO NOT.
✔✔Henderson Hasselbalch Equation: - ✔✔pH = pKa + log [-OAc] / [AcOH]
✔✔Adding acid to water:
What s the pH of 0.01M HCl?
A. 1
B. 2
C. 7
D. 12 - ✔✔-B
✔✔Now lets add 0.01 mol HCL to a bugger that is 1.00M in acetic acid and acetate.
Which part of the buffer will HCl react with?
A. HCl will react with the AcOH
B. HCl will react with the AcO-
C. HCl will react with the water
D. HCl will not react. - ✔✔-B
*HCl will react with the basic part of the buffer.
-So the amount of acid AcOH will increase, and the base -OAc will decrease.
✔✔Now lets add 0.01 mol HCl to a buffer that is 1.00 M in acetic acid and acetate.
What will happen to the pH of the buffer?
A. Increase (a bit)
B. Increase (a lot)
C. Decrease (a bit)
D. Decrease (a lot)
E. HCl will not react. - ✔✔-C
, ✔✔What is the pH of a 0.01M NaOH solution?
A. 2
B. 12
C. 7
D. 14 - ✔✔-B
✔✔ What do you know about reactions? (make a list) - ✔✔-Atoms are conserved. They
are only re-arranged.
-Properties of products are emergent (not a mixture of the reactants properties).
-Reactions can be classified by the type of reaction (how it occurs).
-Reactions are always accompanied by an energy change (can be exo and endo) that
results from changed in interactions (bonds and IMFs) in the reactants and products.
-Reactions are always accompanied by an entropy change.
✔✔What are the two main typed of reactions? - ✔✔-Acid-base
-Redox
*Always accompanied by a changed in entropy.
✔✔Can you predict the properties of products if you know the properties of the
reactants?
A. Yes
B. No
C. It depends
D. I dont know - ✔✔-B
*Properties include smell, melting point, boiling point, and color.
✔✔For the reaction: A+B-->C
If A is yellow and B is blue, what color is C?
A. Yellow
B. Blue
C. Green
D. I dont know - ✔✔-D
*React NOT mix. C = completely new product.
✔✔What thermodynamic function tells you about how far a reaction will "go"?
A. Delta H
B. Delta S (system)
C. Delta G
D. None of these - ✔✔-C
*If (+) will NOT happen.
*If (-) WILL happen.
✔✔What thermodynamic function tells you about how fast a reaction will "go"?
A. Delta H
SOLUTIONS SCORED A+
✔✔Buffer:
Contains boh a weak acid and its conjugate base.
The acid part (HA) will react with any added __________ base.
*HA+B- --> HB + A- (where B- is a strong base, and A- is the weaker conjugate base of
HA)
The base part (A-) will react with and added _________ acid.
*A-+HX --> HA+X- (where HX is a strong acid, and HA is the weaker conjugate acid of
A-). - ✔✔-Strong base.
-Strong acid.
✔✔In effect we are exchanging a strong acid for a week acid- or a strong base for a
weak base- and weak acids or bases ______ _________ affect the pH as much. - ✔✔-
DO NOT.
✔✔Henderson Hasselbalch Equation: - ✔✔pH = pKa + log [-OAc] / [AcOH]
✔✔Adding acid to water:
What s the pH of 0.01M HCl?
A. 1
B. 2
C. 7
D. 12 - ✔✔-B
✔✔Now lets add 0.01 mol HCL to a bugger that is 1.00M in acetic acid and acetate.
Which part of the buffer will HCl react with?
A. HCl will react with the AcOH
B. HCl will react with the AcO-
C. HCl will react with the water
D. HCl will not react. - ✔✔-B
*HCl will react with the basic part of the buffer.
-So the amount of acid AcOH will increase, and the base -OAc will decrease.
✔✔Now lets add 0.01 mol HCl to a buffer that is 1.00 M in acetic acid and acetate.
What will happen to the pH of the buffer?
A. Increase (a bit)
B. Increase (a lot)
C. Decrease (a bit)
D. Decrease (a lot)
E. HCl will not react. - ✔✔-C
, ✔✔What is the pH of a 0.01M NaOH solution?
A. 2
B. 12
C. 7
D. 14 - ✔✔-B
✔✔ What do you know about reactions? (make a list) - ✔✔-Atoms are conserved. They
are only re-arranged.
-Properties of products are emergent (not a mixture of the reactants properties).
-Reactions can be classified by the type of reaction (how it occurs).
-Reactions are always accompanied by an energy change (can be exo and endo) that
results from changed in interactions (bonds and IMFs) in the reactants and products.
-Reactions are always accompanied by an entropy change.
✔✔What are the two main typed of reactions? - ✔✔-Acid-base
-Redox
*Always accompanied by a changed in entropy.
✔✔Can you predict the properties of products if you know the properties of the
reactants?
A. Yes
B. No
C. It depends
D. I dont know - ✔✔-B
*Properties include smell, melting point, boiling point, and color.
✔✔For the reaction: A+B-->C
If A is yellow and B is blue, what color is C?
A. Yellow
B. Blue
C. Green
D. I dont know - ✔✔-D
*React NOT mix. C = completely new product.
✔✔What thermodynamic function tells you about how far a reaction will "go"?
A. Delta H
B. Delta S (system)
C. Delta G
D. None of these - ✔✔-C
*If (+) will NOT happen.
*If (-) WILL happen.
✔✔What thermodynamic function tells you about how fast a reaction will "go"?
A. Delta H
