Acids Quiz #6 Ka’s from pH Kb’s from Ka’s Answers

1. The Kb for the dihydrogen phosphate ion is

A. 1.4 x 10^-12

B. 6.3 x 10^-8

C. 1.6 x 10^-7

D. 7.1 x 10^-3

2. What volume of 0.100 M NaOH is required to neutralize a 10.0 mL sample of 0.200 M H₂SO₄?

A. 5.0 mL

B. 10.0 mL

C. 20.0 mL

D. 40.0 mL

3. Consider the following equilibria:

I	HCO3^-+ H2O ⇄ H2CO3 + OH^-
II	NH4^+ + H2O ⇄ H3O^+ + NH3
III	HSO3^- + H3O ⇄ H2O + H2SO3

Water acts as a Bronsted-Lowry base in

A. III only

B. I and II only

C. II and III only

D. I, II, and III

4. Which of the following is represented by a Kb expression?

A. Al(OH)_3(s) ⇄ Al³⁺_(aq) + 3OH^-_(aq)

B. HF_(aq) + H₂O_(l) ⇄ H₃O⁺_(aq) + F^-_(aq)

C. Cr₂O₇^2-_(aq) + 2OH^-_(aq) ⇄ 2CrO₄^2-_(aq) + H₂O_(l)

D. CH₃NH_2(aq) + H₂O_(l) ⇄ CH₃NH⁺_{3 (aq)}

5. A student combines 0.25 mol of NaOH and 0.20 mol of HCl in water to make 2.0 liters

of solution. The pH of the solution is

A. 1.3

B. 1.6

C. 12.4

D. 12.7

6. If OH^- is added to a solution, the [H₃O⁺] will

A. Remain constant

B. Adjust such that [H₃O⁺]= [OH ^- ]

K_w

C. Increase such that [H₃O⁺][OH^-] = K_w

D. Decrease such that [H₃O⁺][OH^-] = K_w

7. In a titration, 10.0 mL of H₂SO_4(aq) is required to neutralize 0.0400 mol of NaOH.

From this data, the [H₂SO₄] is

A. 0.0200 M

B. 2.00 M

C. 4.00 M

D. 8.00 M

8. Consider the following equilibrium for an acid-base indicator:

Hlnd ⇄ H⁺ + Ind^- K_a = 1.0 x 10^-10

Which of the following statements is correct at pH 7.0?

A. [Ind^-] < [HInd]

B. [Ind^-] = [HInd]

C. [Ind^-] > [HInd]

D. [Ind^-] = [H⁺] = [HInd]

9. Which of the following indicators would be yellow at pH 7 and blue at pH 10?

A. thymol blue

B. methyl violet

C. bromthymol blue

D. bromcresol green

10. Consider the following equilibrium for phenolphthalein: HInd + H⁺ + Ind^-

When phenolphthalein is added to 1.0 M NaOH, the color of the resulting solution is

A. pink as [HInd] is less than [Ind^-]

B. pink as [HInd] is greater than [Ind^-]

C. colorless as [HInd] is less than [Ind^-]

D. colorless as [HInd] is greater than [Ind^-]

11. Water acts as a base when it reacts with

A. CN^-

B. NH₃

C. NO₂^-

D. NH₄⁺

12. What is the pH of a solution prepared by adding 0.50 mol KOH to 1.0 L of 0.30 M

HNO₃?

A. 0.20

B. 0.70

C. 13.30

D. 13.80

13. The 1.0 M acid solution with the largest [H₃O⁺] is

A. HNO₂

B. H₂SO₃

C. H₂CO₃

D. H₃BO₃

14. Consider the following indicator equilibrium:

HInd_(aq) + H₂O_(l) ⇌ H₃O⁺ + Ind^-_(aq)

Colourless blue

What is the effect of adding HCl to a blue sample of this indicator?

Equilibrium Shift Colour Change

A. left less blue

B. left more blue

C. right less blue

D. right more blue

15. Consider the following indicator equilibrium:

HInd_(aq) + H₂O_(l) ⇌ H₃O⁺ + Ind^-_(aq)

Colourless blue

What is the effect of adding NaOH to a light blue sample of this indicator?

Equilibrium Shift Colour Change

A. left less blue

B. left more blue

C. right less blue

D. right more blue

16. Consider the following indicator equilibrium:

HInd_(aq) + H₂O_(l) ⇌ H₃O⁺ + Ind^-_(aq)

yellow blue

What is the effect of adding FeCl₃ to a green sample of this indicator?

Equilibrium Shift Colour Change

A. left yellow

B. left blue

C. right less blue

D. right more blue

17. An indicator has a Ka = 4 x 10^-6. Which of the following is true for this indicator?

pH at Transition Point Indicator

A. 4.0 methyl orange

B. 4.0 bromcresol green

C. 5.4 methyl red

D. 5.4 bromcresol green

18. An indicator has a Ka = 6.3 x 10^-13. Which of the following is true for this indicator?

pH at Transition Point Indicator

A. 4.0 methyl orange

B. 4.0 bromcresol green

C. 12.2 alizarin yellow

D. 12.2 indigo carmine

19. A salt forms in the reaction between HF_(aq) and NaOH_(aq). What is the net ionic equation

for the hydrolysis of this salt?

A. NaF_(aq) ® Na⁺_(aq) + F^-_(aq)

B. HF(aq) + H₂O_(l) ⇌ H₃O⁺_(aq) + F^-_(aq)

C. F^-_(aq) + H₂O_(aq) ⇌ HF_(aq) + OH^-_(aq)

D. HF_(aq) + NaOH_(aq) ® NaF_(aq) + H₂O_(l)

20. What is the Ka for the indicator that is yellow in its basic form and blue in its acid form?

A. 6 x 10^-13

B. 2 x 10^-9

C. 2 x 10^-7

D. 3 x 10^-5

21. What term is used to describe the point at which a chemical indicator changes colour?

A. titration point

B. transition point

C. equivalence point

D. stoichiometric point

22. What is the net ionic equation in the reaction between HF_(aq) and NaOH_(aq)?

A. NaF_(aq) ® Na⁺_(aq) + F^-_(aq)

B.        HF(aq)   +   OH^- _(aq) ⇌ F^-_(aq)  +  H₂O_(l)

C. F^-_(aq) + H₂O_(aq) ⇌ HF_(aq) + OH^- _(aq)

D. HF_(aq) + NaOH_(aq) ® NaF_(aq) + H₂O_(l)

23. Consider the ionization of water: 2H₂O ⇌ H₃O⁺ + OH^-

What happens to the pH when KOH 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.

24. Which of the following salt solutions is acidic?

A. NaBr

B. FeCl₃

C. LiCN

D. NaHCO₃

25. Which of the following salt solutions is neutral?

A. NaBr

B. FeCl₃

C. LiCN

D. NaHCO₃

26. What happens to the ion concentrations in water when a small amount of HBr_(aq) is

added?

A. [H₃O⁺] = [OH^-] = 1.0 x 10-7 M

B. [H₃O⁺] and [OH^-] both increase

C. [H₃O⁺] increases and [OH^-] decreases

D. [H₃O⁺] increases and [OH^-] is unchanged

27. What is the Kb value for H₂PO₄^- ?

A. 1.3 x 10^-12

B. 6.2 x 10^-8

C. 1.6 x 10^-7

D. 2.5 x 10³

28. What is one of the Ka values for thymol blue?

A. 2 x 10^-9

B. 2 x 10^-7

C. 1 x 10^-7

D. 5 x 10²

29. Consider the indicator equilibrium:

HInd_(aq) + H₂O_(l) ⇌ H₃O⁺ + Ind^-_(aq)

yellow blue

Which of the following is true about the transition point of this indicator?

A. pH = 7.0

B.        [HInd]  = [ Ind^- ]

C. [HInd] > [ Ind^- ]

D. moles of H₃O⁺ moles of Ind^-

30. What is the [OH^-] in 0.25 M HCl ?

A. 2.5 x 10^-15 M

B. 4.0 x 10^-14 M

C. 2.5 x 10^-1 M

D. 2.5 x 10^-13 M