Acids Quiz #7 pH Relationships, Amphiprotic Calculations

1. In water, the hydrogen phosphate ion, HPO₄^2-, will act as

A. An acid because K_a < K_b

B. An acid because K_a > K_b

C. A base because K_a < K_b

D. A base because K_a > K_b

2. A student records the pH of 1.0 M solution of two acids

Acid	pH
X	4.0
Y	2.0

Which of the following statements can be concluded from the above data?

A. Acid X is stronger than acid Y

B. Acid X and acid Y are both weak

C. Acid X is diprotic while acid Y is monoprotic

D. Acid X is 100 times more concentrated than acid Y

3. When added to water, the hydrogen carbonate ion, HCO₃^-, produces a solution,

which is

A. basic because K_b is greater than K_a

B. basic because K_a is greater than K_b

C. acidic because K_a is greater than K_b

D. acidic because K_b is greater than K_a

4. The concentration, Ka and pH values of four acids are given in the following table

ACID	Concentration	Ka	pH
HA	3.0 M	2.0 x 10^-5	2.1
HB	0.7 M	4.0 x 10^-5	2.3
HC	4.0 M	1.0 x 10^-5	2.2
HD	1.5 M	1.3 x 10^-5	2.4

Based on this data, the strongest acid is

A. HA

B. HB

C. HC

D. HD

5. Which of the following 0.10 M solutions is the most acidic?

A. AlCl₃

B. FeCl₃

C. CrCl₃

D. NH₄Cl

6. Which of the following acid-base indicators has a transition point between pH 7

and pH 9?

A. Ethyl red, K_a = 8 x 10^-2

B. Congo red, K_a = 9.0 x 10^-3

C. Cresol red, K_a = 1.0 x 10^-8

D. Alizarin blue, K_a = 7.0 x 10^-11

7. Which of the following would be a typical pH of lemon juice?

A. 1.0

B. 3.0

C. 6.8

D. 7.2

8. What is the [KOH] in a KOH solution that has a pH = 13.00?

A. 0.10 M

B. 0.56 M

C. 1.0 M

D. 1.0 x 10^-13 M

9. What is the [H₃O⁺] in 0.70 M HCN ?

A. 0.70 M

B. 1.9 x 10^-5 M

C. 1.0 x 10^-7 M

D. 3.4 x 10^-10 M

10. The S^2- ion is a base with an equilibrium constant of 0.77, what is the Ka value

for HS^-?

A. 1.3 x 10^-14

B. 9.1 x 10^-8

C. 1.1 x 10^-7

D. 7.7 x 10¹³

11. Which of the following is true as a result of the predominant hydrolysis of

NaHCO₃?

Solution Reason

A. basic Ka > Kb

B. basic Ka < Kb

C. acidic Ka > Kb

D. acidic Ka < Kb

12. Consider the ionization of water: H₂O + H₂O ⇌ H₃O⁺ + OH^-

What happens to the pH when 0.1 M NaOH is added to water?

A. pH increases since [H₃O⁺] increases.

B. pH increases since [H₃O⁺] decreases.

C. pH decreases since [H₃O⁺] increases.

D. pH decreases since [H₃O⁺] decreases.

13. Which of the following amphiprotic ions will act predominantly as a base in

solution?

A. HSO₃^-

B. HSO₄^-

C. H₂PO₄^-

D. HPO₄^2-

14. Which of the following statements is true for a alkaline solution at 25 ⁰C ?

A. pH < 7.0

B. pOH > 7.0

C. [H₃O⁺] > [OH^-]

D. [H₃O⁺] < [OH^-]

15. What is the [OH^-] in 0.025 M HCl ?

A. 2.5 x 10^-16 M

B. 4.0 x 10^-13 M

C. 2.5 x 10^-2 M

D. 2.5 x 10^-12 M

16. Which of the following statements is true for an acidic solution at 25 ⁰C ?

A. pH > 7.0

B. pOH < 7.0

C. [H₃O⁺] < [OH^-]

D. [H₃O⁺] > [OH^-]

17. What is the [H⁺] in 0.025 M NaOH?

A. 2.5 x 10^-16 M

B. 4.0 x 10^-13 M

C. 2.5 x 10^-2 M

D. 2.5 x 10^-12 M

18. What [H₃O⁺] results when 25 mL of 1.0 M HCl is mixed with 10 mL of

2.0 M KOH ?

A. 0.70 M

B. 0.00 M

C. 0.10 M

D. 0.14 M

19. What is the pH of 0.70 M HCN ?

A. 0.70 M

B. 1.9 x 10^-5 M

C. 5.32

D. 4.73

20. Consider the following indicator equilibrium:

HInd + H₂O ⇌ H₃O⁺ + Ind^-                      yellow                                      blue

What is the result of adding FeCl₃ to this indicator?

Equilibrium Shift Colour

A. left blue

B. left yellow

C. right blue

D. right yellow

21. An indicator changes colour when 1.0 M HCl is added. If the indicator has a

Ka = 1.0 x 10^-10, determine the indicator and the pH at its transition point.

Indicator pH

A. phenolphthalein 4.0

B. phenolphthalein 10.0

C. thymolphthalein 4.0

D. thymolphthalein 10.0

22. What is the Kb value for HC₆H₅O₇^2- ?

A. 1.0 x 10^-14

B. 5.9 x 10^-10

C. 2.4 x 10^-8

D. 4.1 x 10⁷

23. What is produced when MgO is added to water?

A. the metal Mg

B. the acid HMgO

C. the base Mg(OH)₂

D. the amphiprotic species HMgO₂

24. Which of the following is a major source of NO_2(g), which contributes to

the problem of acid rain?

A. a smelter

B. an air conditioner

C. a nuclear power plant

D. the automobile engine

25. The indicator bromothymol blue can be described by the following equilibrium

equation:

HInd + H₂O ⇌ H₃O⁺ + Ind^-                         yellow   blue

A base is added to the above indicator. After equilibrium has been re-established,

how do the H₃O⁺ and the colour of the solution compare with the original

equilibrium?

H₃O⁺ Colour of Solution

A. decreases turns blue

B. decreases turns yellow

C. increases turns blue

D. increases turns yellow

26. The indicator bromothymol blue can be described by the following equilibrium

equation:

HInd + H₂O ⇌ H₃O⁺ + Ind^-                         yellow   blue

An acid is added to the above indicator. After equilibrium has been re-established,

how do the H₃O⁺ and the colour of the solution compare with the original

equilibrium?

H₃O⁺ Colour of Solution

A. decreases turns blue

B. decreases turns yellow

C. increases turns blue

D. increases turns yellow

27. What is the Ka value for the indicator neutral red?

A. 1 x 10^-14

B. 4 x 10^-8

C. 7.4

D. 14.0

28. What is a common source of SO_2(g) ?

A. automobiles

B. a car battery

C. a lead smelter

D. oxidation of iron

29. What is the [H₃O⁺] in 0.70 M HCN ?

A. 0.70 M

B. 1.9 x 10^-5 M

C. 1.0 x 10^-6 M

D. 2.4 x 10^-10 M

30. What is the value of pKw for water at 25 ⁰C ?

A. 1.0 x 10^-14

B. 10 x 10^-7

C. 7.00

D. 14.00