Chapter 16 3 Calculate the effect of a common-ion on concentrations

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16.2 Algorithmic Questions

1) Which is a net ionic equation for the neutralization of a strong acid with a strong base?

A) HI(aq) + NaOH(aq) ⇌ H2O(l) + NaI(aq)

B) H3O+(aq) + OH–(aq) ⇌ 2 H2O(l)

C) HF(aq) + NaOH(aq) ⇌ H2O(l) + NaF(aq)

D) HCl(aq) + OH–(aq) ⇌ H2O(l) +Cl–(aq)

2) Which is a net ionic equation for the neutralization of a weak acid with a strong base?

A) HBr(aq) + NaOH(aq) ⇌ H2O(l) + NaBr(aq)

B) H3O+(aq) + OH–(aq) ⇌ 2 H2O(l)

C) HF(aq) + LiOH(aq) ⇌ H2O(l) + LiF(aq)

D) HF(aq) + OH–(aq) ⇌ H2O(l) + F–(aq)

3) Which is a net ionic equation for the neutralization reaction of a strong acid with a weak base?

A) HF(aq) + LiOH(aq) ⇌ H2O(l) + LiF(aq)

B) H3O+(aq) + OH–(aq) ⇌ 2 H2O(l)

C) HI(aq) + NH3(aq) ⇌ NH4I(aq)

D) H3O+(aq) + NH3(aq) ⇌ NH4+(aq) + H2O(l)

4) Which is a net ionic equation for the neutralization reaction of a weak acid with a weak base?

A) H3O+(aq) + OH–(aq) ⇌ 2 H2O(l)

B) HF(aq) + NH3(aq) ⇌ NH4+(aq) + F–(aq)

C) HCl(aq) + OH–(aq) ⇌ H2O(l) + Cl–(aq)

D) H3O+(aq) + NH3(aq) ⇌ NH4+(aq) + H2O(l)

5) What is the equation relating the equilibrium constant Kn for the neutralization of a weak acid with a

weak base to the Ka of the acid, the Kb of the base and Kw?

A) Kn = 1/KaKbKw

B) Kn =

C) Kn =

D) Kn =

6) What is the approximate value of the equilibrium constant, Kn, for the neutralization of acetic acid with

potassium hydroxide, shown in the equation below? The Ka for acetic acid is 1.8 × 10-5.

CH3CO2H(aq) + KOH(aq) ⇌ H2O(l) + NaCH3CO2(aq)

A) 1.8 × 10–19

B) 5.6 × 10–10

C) 1.8 × 10–8

D) 1.8 × 109

7) What is the approximate value of the equilibrium constant, Kn, for the neutralization of hydrochloric

acid with sodium hydroxide, shown in the equation below?

HBr(aq) + LiOH(aq) ⇌ H2O(l) + LiBr(aq)

A) 1.0 × 102

B) 1.0 × 107

C) 1.0 × 1014

D) 1.0 × 1028

8) Which of these neutralization reactions has a pH = 7 when equal molar amounts of acid and base are

mixed?

A) CH3CO2H(aq) + LiOH(aq) ⇌ H2O(l) + LiCH3CO2(aq)

B) HI(aq) + C5H5N(aq) ⇌ C5H5NHI(aq)

C) HI(aq) + KOH(aq) ⇌ H2O(l) + KI(aq)

D) HNO2(aq) + NH3(aq) ⇌ NH4NO2(aq)

9) Which of these neutralization reactions has a pH < 7 when equal molar amounts of acid and base are

mixed?

A) CH3CO2H(aq) + NaOH(aq) ⇌ H2O(l) + NaCH3CO2(aq)

B) HCl(aq) + C5H5N(aq) ⇌ C5H5NHCl(aq)

C) HBr(aq) + KOH(aq) ⇌ H2O(l) + KBr(aq)

D) H2SO4(aq) + 2 NaOH(aq) ⇌2 H2O(l) + Na2SO4(aq)

10) Which of these neutralization reactions has a pH > 7 when equal moles of acid and base are mixed?

A) CH3CO2H(aq) + LiOH(aq) ⇌ H2O(l) + LiCH3CO2(aq)

B) HI(aq) + C5H5N(aq) ⇌ C5H5NHI(aq)

C) HCl(aq) + LiOH(aq) ⇌ H2O(l) + LiCl(aq)

D) H2SO4(aq) + 2 KOH(aq) ⇌2 H2O(l) + K2SO4(aq)

11) What is the hydronium ion concentration in a solution prepared by mixing 50.00 mL of 0.10 M HCN

with 50.00 mL of NaCN? Assume that the volumes of the solutions are additive and that Ka =

4.9 × 10–10 for HCN.

A) 4.9 × 10–11 M

B) 4.9 × 10–10 M

C) 4.9 × 10–9 M

D) 7.0 × 10-6 M

12) What is the pH of a solution prepared by mixing 25.00 mL of 0.10 M CH3CO2H with 25.00 mL of

0.040 M CH3CO2Na? Assume that the volume of the solutions are additive and that Ka = 1.8 × 10-5 for

CH3CO2H.

A) 2.87

B) 4.35

C) 4.75

D) 5.14

13) What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M NH3 with 20.00 mL of 0.10 M

NH4Cl? Assume that the volume of the solutions are additive and that Kb = 1.8 × 10–5 for NH3.

A) 8.86

B) 10.26

C) 9.65

D) 11.13

14) What is the pH of a solution prepared by mixing 50.00 mL of 0.10 M methylamine, CH3NH2, with

15.00 mL of 0.10 M methylammonium chloride, CH3NH3Cl? Assume that the volume of the solutions are

additive and that Kb = 3.70 × 10-4 for methylamine.

A) 10.04

B) 10.57

C) 11.09

D) 11.78

15) What is the common ion in a solution prepared by mixing 0.55 M LiCH3CO2 with 0.10 M CH3CO2H?

A) H3O+

B) Li+

C) CH3CO2–

D) OH–

16) When 70 mL of 0.18 M NH4Cl is added to 70 mL of 0.18 M NH3, relative to the pH of the 0.10 M NH3

solution the pH of the resulting solution will

A) become 7.

B) decrease.

C) increase.

D) remain the same.

17) When 110 mL of 0.12 M NaF is added to 110 mL of 0.12 M HF, relative to the pH of the 0.10 M HF

solution the pH of the resulting solution will

A) become 7.

B) decrease.

C) increase.

D) remain the same.

18) What is the pH of a buffer system prepared by dissolving 10.70 grams of NH4Cl and 30.00 mL of 12 M

NH3 in enough water to make 1.000 L of solution? Kb = 1.80 × 10–5 for NH3.

A) 9.00

B) 9.26

C) 9.51

D) 11.32

19) What is the [CH3CO2–]/[CH3CO2H] ratio necessary to make a buffer solution with a pH of 4.24? Ka =

1.8 × 10–5 for CH3CO2H.

A) 0.31:1

B) 0.89:1

C) 1.1:1

D) 3.2:1

20) When equal molar amounts of the following sets of compounds are mixed in water, which will not

form a buffer solution?

A) KH2PO4 with K2HPO4

B) NH3 with NH4I

C) CH3CO2H with LiCH3CO2

D) HNO3 with LiNO3

21) Which of the following combinations of chemicals could be used to make a buffer solution?

A) HCl/KOH

B) HCl/NH3

C) HBr/H3PO4

D) KOH/NH3

22) Calculate the pH of the solution when 0.035 moles of OH– have been added to a 2.0 L containing equal

amounts of 0.10 M acetic acid and 0.10 M sodium acetate. (pKa of acetic acid is 4.76)

A) 5.08

B) 4.91

C) 4.89

D) 4.83

23) What volume of 5.00 × 10-3 M HNO3 is needed to titrate 20.00 mL of 5.00 × 10-3 M Ca(OH)2 to the

equivalence point?

A) 2.50 mL

B) 10.0 mL

C) 20.0 mL

D) 40.0 mL

24) What is the pH of a solution made by mixing 20.00 mL of 0.100 M HCl with 40.00 mL of 0.100 M

KOH? Assume that the volumes of the solutions are additive.

A) 0.48

B) 1.48

C) 12.52

D) 13.52

25) What is the approximate pH at the equivalence point of a weak acid–strong base titration if 25 mL of

aqueous formic acid requires 29.80 mL of 0.2567 M NaOH? Ka = 1.8 × 10-4 for formic acid.

A) 2.13

B) 5.56

C) 8.44

D) 11.87

26) What is the approximate pH at the equivalence point of a weak acid–strong base titration if 25 mL of

aqueous hydrofluoric acid requires 30.00 mL of 0.100 M NaOH? Ka = 6.76 × 10-4 for HF.

A) 2.05

B) 6.05

C) 7.95

D) 11.95

27) Formic acid (HCO2H, Ka = 1.8 × 10-4) is the principal component in the venom of stinging ants. What

is the molarity of a formic acid solution if 25.00 mL of the formic acid solution requires 44.80 mL of 0.0567

M NaOH to reach the equivalence point?

A) 0.0134 M

B) 0.0316 M

C) 0.0567 M

D) 0.102 M

28) What is the pH of the resulting solution if 40.00 mL of 0.10 M acetic acid is added to 10.00 mL of 0.10

M NaOH? Assume that the volumes of the solutions are additive. Ka = 1.8 × 10–5 for CH3CO2H.

A) 9.73

B) 8.78

C) 5.22

D) 4.27

29) What is the pH of a solution made by mixing 5.00 mL of 0.10 M acetic acid with 5.00 mL of 0.10 M

KOH? Assume that the volumes of the solutions are additive. Ka = 1.8 × 10-5 for CH3CO2H.

A) 5.28

B) 7.00

C) 8.72

D) 10.02

30) What is the pH of a solution made by mixing 30.00 mL of 0.10 M acetic acid with 45.00 mL of 0.100 M

KOH? Assume that the volumes of the solutions are additive. Ka = 1.8 × 10–5 for CH3CO2H.

A) 8.26

B) 9.26

C) 11.13

D) 12.30

31) Which of the following titrations result in a basic solution at the equivalence point?

A) HCl titrated with LiCH3CO2

B) HOCl titrated with KOH

C) HI titrated with LiOH

D) Pb(NO3)2 titrated with NaI

32) The equivalence point pH of the titration of four weak acids is given. Which is the strongest acid?

A) 7.18

B) 7.90

C) 8.14

D) 8.43

33) Sodium hypochlorite, NaOCl, is the active ingredient in household bleach. What is the concentration

of hypochlorite ion if 20.00 mL of bleach requires 31.00 mL of 0.500 M HCl to reach the equivalence point?

A) 0.275 M

B) 0.333 M

C) 0.775 M

D) 1.28 M

34) What is the pH at the equivalence point of a weak base-strong acid titration if 20.00 mL of NaOCl

requires 28.30 mL of 0.20 M HCl? Ka = 3.0 × 10-8 for HOCl.

A) 0.70

B) 3.39

C) 3.76

D) 4.23

35) What is the pH of the resulting solution if 40. mL of 0.432 M methylamine, CH3NH2, is added to 15

mL of 0.234 M HCl? Assume that the volumes of the solutions are additive. Ka = 2.70 × 10–11 for

CH3NH3+.

A) 2.84

B) 4.02

C) 9.97

D) 11.16

36) Which of the following titrations result in an acidic solution at the equivalence point?

A) CH3COOH titrated with LiOH

B) NaF titrated with LiOH

C) HBr titrated with KOH

D) C5H5N titrated with HCl

37) The equivalence point pH of the titration of four weak bases is given. Which is the strongest base?

A) 4.20

B) 6.10

C) 6.40

D) 7.90