Deck 15: Acid-Base Equilibria

Question 1

Which of the following is a Lewis acid?

A) Fe²⁺
B) BH₃
C) NH₃
D) a and b
E) a and c

Answer 1

D

Question 2

The value of K_w increases slightly over the temperature range 0 to 60°C. Compared to its value at 0°C, the pH of water at room temperature will be:

A) higher
B) lower
C) the same
D) not enough data to answer the question

Answer 2

B

Question 3

The value of K_w increases slightly over the temperature range 0 to 60°C. Compared to its value at 0°C, the pH of water at room temperature will be:

A) higher
B) lower
C) the same
D) not enough data to answer the question

Answer 3

B

Question 4

Which of the following is the strongest acid:

A) NH₃
B) PH₃
C) Both are equally strong
D) Not enough data to answer the question

Question 5

In pure water:

A) There are no detectible ions in solution
B) There are detectible ions in solution
C) H₃O⁺ and OH^- ions are more prevalent than H₂O molecules
D) a and c
E) b and c

Question 6

K_a = 6.6×10^-4 for the reaction:
HF + H₂O H₃O⁺ + F^-
What is K_b for the reaction?
F^- + H₂O HF + OH^-

A) 6.6×10^-4
B) 1.6×10⁴
C) 6.6×10^-18
D) 1.5×10^-11

Question 7

Which of the following is the titration curve of strong acid being titrated by a strong base

A)

B)

C)

D)

Question 8

Which of the following is the titration curve of weak base being titrated by a strong acid

A)

B)

C)

D)

Question 9

Exhibit 15-1
The following question(s) pertain to the titration of 50.0 ml of HNO₃ with NaOH as depicted in the plot below. Refer to Exhibit 15-1. Estimate the initial concentration of Nitric Acid

A) 0.50 M
B) 0.32 M
C) 1.0 M
D) 15.0 M

Question 10

Exhibit 15-1
The following question(s) pertain to the titration of 50.0 ml of HNO₃ with NaOH as depicted in the plot below. Refer to Exhibit 15-1. Estimate the initial concentration of Sodium Hydroxide

A) 0.38 M
B) 0.42 M
C) 0.60 M
D) 0.55 M

Question 11

A student has 100.0 ml of 0.65 M HCl. What is the pH of this solution?

A) 1.39
B) 0.187
C) 6.50
D) 13.8
E) None of the above

Question 12

A student has 50.0 ml of 0.30 M NaOH. What is the pH of this solution?

A) 1.82
B) 11.00
C) 0.523
D) 2.0
E) None of the above

Question 13

A student mixes 60.0 ml of 0.30 M NaOH with 20.0 ml of 0.90 M HCl. What is the pH of the resulting solution?

A) 0
B) 14
C) 7
D) 1.27
E) None of the above

Question 14

Based on the plot below, estimate the value of K_a for the weak acid.

A) 4.7
B) 2.0×10^-5
C) 2.6
D) 2.5×10^-3
E) None of the above

Question 15

Exhibit 15-2
The following question(s) pertain to the sequence of events below:
Part A: A solution initially only containing 500.0 ml of 1.00 M Formic Acid.
Part B: 800.0 ml of 0.500 M NaOH is added to the solution from Part A.
Part C: An additional 250.0 ml of the 0.500 M NaOH is added to the resulting solution from Part B.
Refer to Exhibit 15-2,Part A. What is the pH of the solution?

A) 3.75
B) 1.83
C) 0
D) None of the above

Question 16

Exhibit 15-2 The following question(s) pertain to the sequence of events below:
Part A: A solution initially only containing 500.0 ml of 1.00 M Formic Acid.
Part B: 800.0 ml of 0.500 M NaOH is added to the solution from Part A.
Part C: An additional 250.0 ml of the 0.500 M NaOH is added to the resulting solution from Part B.
Refer to Exhibit 15-2, Part B. What is the resulting pH?

A) 1.11
B) 4.35
C) 3.15
D) None of the above

Question 17

Exhibit 15-2 The following question(s) pertain to the sequence of events below:
Part A: A solution initially only containing 500.0 ml of 1.00 M Formic Acid.
Part B: 800.0 ml of 0.500 M NaOH is added to the solution from Part A.
Part C: An additional 250.0 ml of the 0.500 M NaOH is added to the resulting solution from Part B.
Refer to Exhibit 15-2, Part C. What is the new pH?

A) 3.05
B) 10.94
C) 12.20
D) 13.33

Question 18

A student dissolves 30.00 grams of sodium acetate in exactly one liter of water. What will be the pH of the resulting solution?

A) 9.68
B) 9.24
C) 9.16
D) 4.84

Question 19

What will have the higher pOH, a 1.0 M solution of sodium acetate of a 1.0 M solution of sodium benzoate?

A) Sodium benzoate
B) Sodium acetate
C) Both pH values will be near 7
D) None of the above

Question 20

A student wants to make a pH 4.0 buffer solution. She decides to use a buffer made from formic acid and sodium formate (NaCOOH). She adds 50.0 grams of sodium formate to a 1 L volumetric flask. How many mL of 3.0 M formic acid should she add to the 1 L volumetric flask so that when the flask is diluted to the mark the pH will be 4.00?

A) 13.8 ml
B) 138 ml
C) 72.6 ml
D) 726 ml
E) None of the above

Question 21

Solutions containing the H₂PO₄^- and HPO₄^2- ions should respectively

A) both be acidic
B) both be basic
C) be acidic and basic
D) be basic and acidic

Question 22

Exhibit 15-3
The following question(s) pertain to a solution made by combining benzoic acid and sodium benzoate. The final volume of the solution is 1.00 L and the initial concentrations of benzoic acid and sodium benzoate are 0.50 and 0.70 respectively.
Refer to Exhibit 15-3. When adding strong acid to this solution:

A) the benzoic acid concentration should rise and the benzoate concentration should fall
B) the benzoic acid concentration should fall and the benzoate concentration should rise
C) both benzoic acid and sodium benzoate concentrations should fall
D) the concentration of all ions should remain roughly constant
E) None of the above

Question 23

Exhibit 15-3
The following question(s) pertain to a solution made by combining benzoic acid and sodium benzoate. The final volume of the solution is 1.00 L and the initial concentrations of benzoic acid and sodium benzoate are 0.50 and 0.70 respectively.
Refer to Exhibit 15-3. What is pH of this solution?

A) 4.04
B) 4.19
C) 4.33
D) 9.81
E) None of the above

Question 24

Exhibit 15-3
The following question(s) pertain to a solution made by combining benzoic acid and sodium benzoate. The final volume of the solution is 1.00 L and the initial concentrations of benzoic acid and sodium benzoate are 0.50 and 0.70 respectively.
Refer to Exhibit 15-3. Calculate the pH after the addition of 500 ml of 1.00 M HCl.

A) 0.175
B) 0.876
C) 3.48
D) 4.89
E) None of the above

Question 25

Exhibit 15-3
The following question(s) pertain to a solution made by combining benzoic acid and sodium benzoate. The final volume of the solution is 1.00 L and the initial concentrations of benzoic acid and sodium benzoate are 0.50 and 0.70 respectively.
Refer to Exhibit 15-3. Calculate the pH after the addition of an additional 250 ml of 1.00 M HCl.

A) 0.339
B) 1.54
C) 2.98
D) 5.38
E) None of the above

Question 26

Exhibit 15-4
The following question(s) pertain to a solution prepared by combining 1.0 mole of ammonia and 50.0 grams of ammonium nitrate in enough water to give a final volume of 2.00 liters.
Refer to Exhibit 15-4. When adding strong acid to this solution:

A) the ammonia concentration should rise
B) the ammonium ion concentration should fall
C) both a and b
D) None of the above

Question 27

Exhibit 15-4
The following question(s) pertain to a solution prepared by combining 1.0 mole of ammonia and 50.0 grams of ammonium nitrate in enough water to give a final volume of 2.00 liters.
Refer to Exhibit 15-4. What is pH of this solution?

A) 9.46
B) 9.55
C) 9.04
D) 4.95
E) None of the above

Question 28

Exhibit 15-4
The following question(s) pertain to a solution prepared by combining 1.0 mole of ammonia and 50.0 grams of ammonium nitrate in enough water to give a final volume of 2.00 liters.
Refer to Exhibit 15-4. Calculate the pH after the addition of 500 ml of 1.00 M HCl.

A) 4.40
B) 5.10
C) 8.90
D) 9.04
E) None of the above

Question 29

Exhibit 15-4
The following question(s) pertain to a solution prepared by combining 1.0 mole of ammonia and 50.0 grams of ammonium nitrate in enough water to give a final volume of 2.00 liters.
Refer to Exhibit 15-4. Calculate the pH after the addition of an additional 250 ml of 1.00 M HCl.

A) 0.266
B) 2.51
C) 4.76
D) 7.75
E) None of the above

Question 30

Predict whether a 0.500 M aqueous solution of sodium hydrogen sulfite (NaHSO₃) should be acidic, basic, or neutral.

A) acidic
B) neutral
C) basic

Question 31

A solution is prepared by mixing hydrazoic acid (HN₃) and NaN₃ and then allowed to come to equilibrium. Upon addition of sulfuric acid

A) more NaN₃ will be formed
B) More HN₃ will be formed
C) More N will be formed
D) Both A and B
E) Impossible to answer without knowing equilibrium concentrations

Question 32

You have at your disposal 100.00 mL of 0.650 M HCl and 500.00 mL of 0.300 M NaOH. How many mL of the base have to be added to the full volume of the acid to reach a pH of 1.90?

A) 10.2 mL
B) 20.4 mL
C) 43.3 mL
D) 204 mL
E) 433 mL

Question 33

Which of the following titration curves schematically represents a diprotic acid being titrated by a strong base?

A)

B)

C)

D)

E) None of the above