Deck 18: Principles of Chemical Reactivity: Other Aspects of Aqueous Equilibria

Question 1

A certain weak base B has a base-ionization constant K_b of 5.9 × 10^-4 at 25°C. If strong acid is added to a solution of B, at what pH will [B] = [BH⁺]?

A) 8.5
B) 10.8
C) 7.0
D) 3.2
E) 5.5

Answer 1

10.8

Question 2

What will be the pH of the solution when 0.10 mol of H⁺ ion is added to a 2.0 liter buffered solution composed of 0.45 M ammonia, NH3, and 0.26 M ammonium fluoride, NH₄F? (K_b for ammonia = 1.8 × 10^-5)

A) 8.07
B) 4.63
C) 9.37
D) 10.34
E) 4.85

Answer 2

9.37

Question 3

What is the pH of the buffer that results when 12.0 g of NaH₂PO₄ and 8.00 g of Na₂HPO₄ are diluted with water to a volume of 0.50 L? (K_a of H₂PO₄^- = 6.2 × 10^-8, the molar masses of NaH₂PO₄ and Na₂HPO₄ are 120.0 g/mol and 142.0 mol, respectively)

A) 4.10
B) 6.96
C) 7.21
D) 7.46
E) 9.90

Answer 3

4.10

Question 4

What is the pH of a buffer that results when 0.50 mole of H₃PO₄ is mixed with 0.75 mole of NaOH and diluted with water to 1.00 L? (The acid dissociation constants of phosphoric acid are K_a1 = 7.5 × 10^-3, K_a2 = 6.2 × 10^-8, and K_a3 = 3.6 × 10^-13)

A) 1.82
B) 2.12
C) 6.91
D) 7.21
E) 12.44

Question 5

If 20 mL of 0.10 M NaOH is added to 40 mL of 0.20 M HC₂H₃O₂, what is the pH of the resulting solution at 25°C? K_a for HC₂H₃O₂ is 1.8 × 10^-5 at 25°C.

A) 9.8
B) 4.1
C) 5.2
D) 2.7
E) 4.3

Question 6

All of the following statements concerning acid-base buffers are true EXCEPT

A) buffers are resistant to pH changes upon addition of small quantities of strong acids or bases.
B) buffers are used as colored indicators in acid-base titrations.
C) the pH of a buffer is close to the pK_a of the weak acid from which it is made.
D) buffers contain appreciable quantities of a weak acid and its conjugate base.
E) buffers are resistant to changes in pH when diluted with water.

Question 7

A 1.0 liter solution contains 0.25 M hydrogen fluoride (HF) and 0.38 M sodium fluoride (NaF). What is the pH of this solution? (K_a for HF is 7.2 × 10^-4)

A) 3.14
B) 3.32
C) 2.96
D) 0.18
E) 10.68

Question 8

What is the pH of an aqueous solution composed of 0.64 M NH₄⁺ and 0.20 M NH₃? (K_a of NH₄⁺ = 5.6 × 10^-10)

A) 4.80
B) 8.75
C) 9.20
D) 9.25
E) 9.76

Question 9

What is the pH of a buffer that results when 0.50 mole of H₃PO₄ is mixed with 0.25 mole of NaOH and diluted with water to 1.00 L? (The acid dissociation constants of phosphoric acid are K_a1 = 7.5 × 10^-3, K_a2 = 6.2 × 10^-8, and K_a3 = 3.6 × 10^-13)

A) 1.82
B) 2.12
C) 6.91
D) 7.21
E) 12.44

Question 10

Which of the following mathematical expressions is the Henderson-Hasselbalch equation?

A) $\mathrm { p } K _ { \mathrm { a } } = \mathrm { pH } + \log \left( \frac { [ \text { conjugate base } ] } { [ \text { acid } ] } \right)$
B) $\mathrm { pH } = \mathbf { p } K _ { \mathrm { a } } + \log \left( \frac { \left[ \mathrm { OH } ^ { - } \right] } { \left[ \mathrm { H } _ { 3 } \mathrm { O } ^ { + } \right] } \right)$
C) $\mathrm { pH } = \mathrm { p } K _ { \mathrm { a } } + \log \left( \frac { [ \text { acid } ] } { [ \text { conjugate base } ] } \right)$
D) $\mathrm { p } K _ { \mathrm { a } } = \mathrm { pH } + \log \left( \frac { \left[ \mathrm { OH } ^ { - } \right] } { \left[ \mathrm { H } _ { 3 } \mathrm { O } ^ { + } \right] } \right)$
E) $\mathrm { pH } = \mathbf { p } K _ { \mathrm { a } } + \log \left( \frac { [ \text { conjugate base } ] } { [ \text { acid } ] } \right)$

Question 11

What is the pH of a solution made by combining 134 mL of 0.26 M NaC₂H₃O₂ with 211 mL of 0.31 M HC₂H₃O₂? The K_a of acetic acid is 1.75 × 10^-5.

A) 4.47
B) 5.04
C) 5.52
D) 4.42
E) 4.97

Question 12

If 25 mL of 0.10 M NaOH is added to 40 mL of 0.20 M HC₂H₃O₂, what is the pH of the resulting solution at 25°C? K_a for HC₂H₃O₂ is 1.8 × 10^-5 at 25°C.

A) 10.1
B) 4.2
C) 5.1
D) 2.7
E) 4.4

Question 13

Which of the following combinations would be best to buffer an aqueous solution at a pH of 9.24?

A) H₃PO₄ and H₂PO₄^-, K_a1 = 7.5 × 10^-3
B) HNO₂ and NO₂^-, K_a = 4.5 × 10^-4
C) CH₃CO₂H and CH₃COO^-, K_a = 1.8 × 10^-5
D) H₂PO₄^- and HPO₄^2-, K_a2 = 6.2 × 10^-8
E) NH₄⁺ and NH₃, K_a = 5.7 × 10^-10

Question 14

When mixed in appropriate amounts, each of the following mixtures can produce an effective buffer solution except _____.

A) HCl and NaH₂PO₄
B) Na₂HPO₄ and Na₃PO₄
C) NaHCO₃ and Na₂CO₃
D) NaH₂PO₄ and Na₂HPO₄
E) NaOH and NaF

Question 15

What is the pH of a solution that is 0.044 M in HA and also 0.0044 M in NaA? (K_a = 4.7 × 10^-6)

A) 8.12
B) 4.33
C) 6.33
D) 5.33
E) 7.74

Question 16

What is the pH of the buffer that results when 32 g sodium acetate (NaCH₃CO₂) is mixed with 500.0 mL of 1.0 M acetic acid (CH₃CO₂H) and diluted with water to 1.0 L? (K_a of CH₃CO₂H = 1.8 × 10^-5)

A) 2.52
B) 4.23
C) 4.44
D) 4.64
E) 4.74

Question 17

What is the pH of a buffer that results when 0.40 mol NaHCO₂ is mixed with 100.0 mL of 2.00 M HCl(aq) and diluted with water to 250 mL? (K_a of HCO₂H = 1.8 × 10^-4)

A) −0.301
B) 3.05
C) 3.44
D) 3.74
E) 4.05

Question 18

What is the pH of a buffer composed of 0.35 M H₂PO₄^-(aq) and 0.65 M HPO₄^2-(aq)? (K_a of H₂PO₄^- is 6.2 × 10^-8)

A) 6.94
B) 7.21
C) 7.48
D) 7.73
E) 9.06

Question 19

A 1.0-liter solution contains 0.25 M HF and 0.33 M NaF (K_a for HF is 7.2 × 10^-4). If one adds 0.30 liters of 0.020 M KOH to the solution, what will be the change in pH?

A) 0.02
B) 3.28
C) 0.14
D) -0.11
E) -0.28

Question 20

Calculate the pH of a solution made by mixing 100.0 mL of 0.627 M NH₃ with 100.0 mL of 0.100 M HCl. (K_b for NH₃ = 1.8 × 10^-5)

A) 9.98
B) 4.02
C) 8.53
D) 9.26
E) none of these

Question 21

You have 75.0 mL of 0.17 M HA. After adding 30.0 mL of 0.10 M NaOH, the pH is 5.50. What is the K_a value of HA?

A) 3.2 × 10^-6
B) 9.7 × 10^-7
C) 0.31
D) 7.4 × 10^-7
E) none of these

Question 22

What mass of sodium hydroxide must be added to 65.0 mL of 0.926 M acetic acid in order to create a buffer with a pH of 4.83? K_a for acetic acid is 1.8 × 10^-5.

A) 49 g
B) 1.3 g
C) 1.0 g
D) 0 g
E) 2.4 g

Question 23

A volume of 25.0 mL of 0.100 M C₆H₅CO₂H(aq) is titrated with 0.100 M NaOH(aq). What is the pH after the addition of 12.5 mL of NaOH? (K_a of benzoic acid = 6.3 × 10^-5)

A) 2.60
B) 4.20
C) 5.40
D) 7.00
E) 8.60

Question 24

A 50.00-mL solution of 0.0400 M hydrofluoric acid (K_a = 7.2 × 10^-4) is titrated with a 0.0153 M solution of NaOH as the titrant. What is the pH of at the equivalence point? (K_w = 1.00 × 10^-14)

A) 7.59
B) 11.45
C) 6.41
D) 10.86
E) 3.14

Question 25

A buffer contains 0.50 mol NH₄⁺ and 0.50 mol NH₃ diluted with water to 1.0 L. How many moles of NaOH are required to increase the pH of the buffer to 10.00? (pK_a of NH₄⁺ = 9.25)

A) 0.035 mol
B) 0.15 mol
C) 0.35 mol
D) 0.41 mol
E) 2.8 mol

Question 26

If 0.50 L of a buffer containing 1.0 mol H₂PO₄− and 1.0 mol HPO₄²⁻ is diluted to a volume of 5.0 L, the pH

A) increases by 1.
B) decreases by 1.
C) increases by 10.
D) decreases by 10.
E) remains unchanged.

Question 27

Consider the titration of 300.0 mL of 0.414 M NH₃ (K_b = 1.8 ×10^-5) with 0.500 M HNO₃. After 150.0 mL HNO₃ has been added, what is the pH of the solution?

A) 4.93
B) 9.07
C) 6.07
D) 11.07
E) 7.00

Question 28

A 50.00-mL solution of 0.0426 M trimethylamine (K_b = 6.5 × 10^-5) is titrated with a 0.0257 M solution of hydrochloric acid as the titrant. What is the pH of the base solution after 22.31 mL of titrant have been added? (K_w = 1.00 × 10^-14)

A) 11.21
B) 10.23
C) 3.77
D) 4.19
E) 12.63

Question 29

How many moles of HCl must be added to 1.0 L of 1.0 M NH₃(aq) to make a buffer with a pH of 9.00? (pK_a of NH₄⁺ = 9.25)

A) 0.36 mol
B) 0.44 mol
C) 0.56 mol
D) 0.64 mol
E) 1.8 mol

Question 30

When a weak base is titrated with a strong acid, the pH at the equivalence point is _____.

A) less than 7
B) greater than 7
C) equal to 7
D) equal to the acid pK_a
E) equal to the base pK_b

Question 31

A 50.00-mL solution of 0.0350 M ethylamine (K_b = 5.6 × 10^-4) is titrated with a 0.0135 M solution of hydrochloric acid as the titrant. What is the pH at the equivalence point? (K_w = 1.0 × 10^-14)

A) 10.75
B) 6.38
C) 2.63
D) 3.25
E) 7.62

Question 32

If 25 mL of 0.750 M HCl are added to 100. mL of 0.302 M NaOH, what is the final pH?

A) 12.96
B) 1.04
C) 13.38
D) 0.62
E) 7.00

Question 33

A buffer is composed of 0.400 mol H₂PO₄^- and 0.400 mol HPO₄^2- diluted with water to a volume of 1.00 L. The pH of the buffer is 7.210. How many moles of HCl must be added to decrease the pH to 6.210?

A) 0.200 mol
B) 0.327 mol
C) 0.360 mol
D) 0.400 mol
E) 3.60 mol

Question 34

If the ratio of acid to base in a buffer increases by a factor of 10, the pH of the buffer

A) increases by 1.
B) decreases by 1.
C) increases by 10.
D) decreases by 10.
E) remains unchanged.

Question 35

What is the pH at the equivalence point when a 25.0 mL sample of 0.200 M aqueous formic acid (HCO₂H) is titrated with 0.100 M aqueous potassium hydroxide? (K_a of HCO₂H = 1.8 × 10^-4)

A) 5.71
B) 7.00
C) 8.28
D) 8.52
E) 10.26

Question 36

How many moles of solid NaF would have to be added to 1.0 L of 2.16 M HF solution to achieve a buffer of pH 3.35? Assume there is no volume change. (K_a for HF = 7.2 × 10^-4)

A) 3.5
B) 0.45
C) 0.75
D) 1.0
E) 1.6

Question 37

What mass of solid NaCH₃CO₂ (molar mass = 82.0 g/mol) should be added to 1.0 L of 0.50 M CH₃CO₂H to make a buffer with a pH of 7.21? (pK_a of CH₃CO₂H = 7.21)

A) 0.0 g
B) 1.9 g
C) 41 g
D) 71 g
E) 1.6 × 10² g

Question 38

What molar ratio of acetic acid to sodium acetate is required to create a buffer solution having a pH of 4.88 at 25°C? K_a for HC₂H₃O₂ is 1.8 × 10^-5.

A) 0.73
B) 1.4
C) 0.52
D) 2.0
E) 2.7

Question 39

A 50.0 mL sample of 0.155 M HNO₂(aq) is titrated with 0.100 M NaOH(aq). What is the pH of a solution after the addition of 25.0 mL of NaOH? (K_a of HNO₂ = 4.5 × 10^-4)

A) 3.02
B) 3.22
C) 3.67
D) 3.86
E) 4.05

Question 40

Which acid-base combination is depicted by this titration curve? The dot on the curve is located at the titrant volume where the titration solution pH equals 7.

A) Titration of a strong acid with a strong base.
B) Titration of a strong base with a strong acid.
C) Titration of a weak acid with a strong base.
D) Titration of a weak base with a strong acid.
E) Not enough information provided.

Question 41

A 25.00-mL sample of propionic acid, HC₃H₅O₂, of unknown concentration was titrated with 0.145 M KOH. The equivalence point was reached when 43.02 mL of base had been added. What was the original concentration of the propionic acid?

A) 0.295 M
B) 0.125 M
C) 0.084 M
D) 0.145 M
E) 0.250 M

Question 42

The K_sp of Ca(OH)₂ is 5.5 × 10^-5 at 25 °C. What is the concentration of OH^-(aq) in a saturated solution of Ca(OH)₂(aq)?

A) 1.9 × 10^-3 M
B) 7.4 × 10^-3 M
C) 2.4 × 10^-2 M
D) 4.0 × 10^-2 M
E) 4.8 × 10^-2 M

Question 43

The concentration of calcium carbonate in a saturated aqueous solution at 25°C is $6.71 \times 10 ^ { - 5 }$ M. What is the K_sp of this sparingly soluble salt?

A) $4.5 \times 10 ^ { - 9 }$
B) $1.21 \times 10 ^ { - 12 }$
C) $5.47 \times 10 ^ { - 16 }$
D) $8.19 \times 10 ^ { - 3 }$
E) $4.06 \times 10 ^ { - 2 }$

Question 44

Which of the following indicators is most suitable for the titration of a 25.00-mL sample of 0.140 M propionic acid, HC₃H₅O₂, with strong base?

A) alizarin yellow (transition pH range: 10.0-12.0)
B) methyl red (transition pH range: 4.2-6.3)
C) methyl orange (transition pH range: 3.1-4.4)
D) thymol blue (transition pH range: 8.0-9.6)
E) bromothymol blue (transition pH range: 6.2-7.6)

Question 45

The solubility of manganese(II) carbonate is 5.4 × 10^-4 g/L. What is the solubility product constant for manganese(II) carbonate?

A) 2.2 × 10^-11
B) 4.7 × 10^-6
C) 2.9 × 10^-7
D) 7.7 × 10^-21
E) 4.1 × 10^-16

Question 46

Which is the best colored indicator to use in the titration of 0.1 M CH₃CO₂H(aq) with NaOH(aq)? Why? (K_a of CH₃CO₂H = 1.8 × 10^-5, K_b of CH₃CO₂^- = 5.6 × 10^-10) $$\begin{array} { l l } \text { Indicator } & \mathrm { p } K _ { \mathrm { a } } \\\hline \text { Bromcresol Green } & 4.8 \\\text { Bromthymol Blue } & 6.8 \\\text { Phenolphthalein } & 9.2\end{array}$$

A) Bromcresol Green. The equivalence point for a weak acid titration occurs at low pH.
B) Bromthymol Blue. The pH at the equivalence point is 7.0.
C) Bromcresol Green. The pK_a of CH₃CO₂H and the pK_a of the indicator are similar.
D) Phenolphthalein. The pK_a of CH₃CO₂^- and the pK_b of the indicator are similar.
E) Phenolphthalein. The pH at the equivalence point is near the pK_a of the indicator.

Question 47

Titration of 0.1615 g of an unknown monoprotic acid dissolved in 25.00 mL of water requires 21.84 mL of 0.1231 M NaOH to reach the endpoint. What is the molar mass of the acid?

A) 60 g/mol
B) 0.01665 g/mol
C) 52.46 g/mol
D) 0.9100 g/mol
E) 2.718 g/mol

Question 48

What is the solubility product expression for La(OH)₃?

A) $K _ { \mathrm { sp } } = \left[ \mathrm { La } ^ { 3 + } \right] \left[ 3 \mathrm { OH } ^ { - } \right]$
B) $K _ { \mathrm { sp } } = \left[ \mathrm { La } ^ { 3 + } \right] \left[ 3 \mathrm { OH } ^ { - } \right] ^ { 3 }$
C) ? $K _ { \mathrm { sp } } = \left[ \mathrm { La } ^ { 3 + } \right] \left[ \mathrm { OH } ^ { - } \right] ^ { 3 }$
D) ? $K _ { \mathrm { sp } } = \frac { \left[ \mathrm { La } ^ { 3 + } \right] \left[ \mathrm { OH } ^ { - } \right] } { \left[ \mathrm { La } ^ { 3 + } \left( \mathrm { OH } _ { 3 } \right) \right] }$
E) ? $K _ { \mathrm { sp } } = \frac { \left[ \mathrm { La } ^ { 3 + } \left( \mathrm { OH } _ { 3 } \right) \right] } { \left[ \mathrm { La } ^ { 3 + } \right] \left[ \mathrm { OH } ^ { - } \right] }$

Question 49

An impure sample of sodium carbonate, Na₂CO₃, is titrated with 0.113 M HCl according to the reaction below.
2 HCl(aq) + Na₂CO₃(aq) $\leftrightharpoons$ CO₂(g) + H₂O( $\ell$ ) + 2 NaCl(aq)
What is the percent of Na₂CO₃ in a 0.613 g sample if the titration requires 26.14 mL of HCl? The molar mass of Na₂CO₃ is 106.0 g/mol.

A) 0.295%
B) 15.7%
C) 25.5%
D) 51.1%
E) 67.9%

Question 50

What is the molar solubility of silver(I) iodide at 25°C? The solubility product constant for silver(I) iodide is 8.3 × 10^-17 at 25°C.

A) 9.1 × 10^-9 M
B) 4.2 × 10^-17 M
C) 4.8 × 10^-5 M
D) 2.7 × 10^-6 M
E) 8.3 × 10^-17 M

Question 51

What is the pH of a saturated solution of Fe(OH)₂? (K_sp = 8.0 × 10^-16 and K_w = 1.01 × 10^-14)

A) 4.93
B) 8.77
C) 5.23
D) 9.07
E) 7.00

Question 52

The K_sp of BaSO₄ is 1.1 × 10^-10 at 25 °C. What mass of BaSO₄ will dissolve in 1.0 L of water at 25 °C? (molar mass = 233.4 g/mol)

A) 2.6 × 10−⁸ g
B) 4.5 × 10−⁸ g
C) 1.0 × 10−⁵ g
D) 1.6 × 10−⁴ g
E) 2.4 × 10−³ g

Question 53

The solubility of strontium carbonate (SrCO₃) in water at 25°C is $4.5 \times 10 ^ { - 3 }$ g/L. What is the K_sp of this sparingly soluble salt?

A) $9.3 \times 10 ^ { - 10 }$
B) $1.13 \times 10 ^ { - 13 }$
C) $2.34 \times 10 ^ { - 17 }$
D) $5.52 \times 10 ^ { - 3 }$
E) $3.12 \times 10 ^ { - 2 }$

Question 54

A solution containing 10. mmol of CO₃²⁻ and 5.0 mmol of HCO₃−is titrated with 1.1 M HCl. What total volume of HCl must be added to reach the second equivalence point? (1 mmol = 0.001 mol)

A) 13.6 mL
B) 9.1 mL
C) 4.5 mL
D) 22.7 mL
E) 27.7 mL

Question 55

A 25.0 mL sample of 0.10 M sodium benzoate is titrated with 0.10 M HCl(aq). What is the pH after the addition of 32.0 mL of HCl(aq)? (K_b of C₆H₅CO₂^- = 1.6 × 10^-10)

A) 1.00
B) 1.25
C) 1.91
D) 4.20
E) 9.79

Question 56

What is the concentration of silver(I) ion in a saturated solution of silver(I) carbonate containing 0.0072 M Na₂CO₃? For Ag₂CO₃, K_sp = 8.6 × 10^-12.

A) 6.0 × 10^-4 M
B) 2.0 × 10^-9 M
C) 8.0 × 10^-9 M
D) 3.5 × 10^-5 M
E) 8.0 × 10^-4 M

Question 57

What color change is exhibited by phenolphthalein during a titration of aqueous acetic acid with aqueous sodium hydroxide?

A) Colorless to pink
B) Pink to colorless
C) Green to yellow
D) Yellow to blue
E) Blue to yellow

Question 58

A solution containing 10. mmol of CO₃²⁻and 5.0 mmol of HCO₃−is titrated with 1.1 M HCl. What volume of HCl must be added to reach the first equivalence point? (1 mmol = 0.001 mol)

A) 24.1 mL
B) 4.5 mL
C) 9.1 mL
D) 19.1 mL
E) 14.1 mL

Question 59

The hydroxide ion concentration of a saturated solution of Fe(OH)₂ is $1.16 \times 10 ^ { - 5 }$ M. What is the solubility product constant for Fe(OH)₂?

A) $7.9 \times 10 ^ { - 16 }$
B) $6.32 \times 10 ^ { - 15 }$
C) $1.58 \times 10 ^ { - 15 }$
D) $3.41 \times 10 ^ { - 3 }$
E) $2.27 \times 10 ^ { - 2 }$

Question 60

Potassium hydrogen phthalate (KHP) is used to standardize sodium hydroxide. If 35.39 mL of NaOH(aq) is required to titrate 0.8246 g KHP to the equivalence point, what is the concentration of the NaOH(aq)? (The molar mass of KHP = 204.2 g/mol) HC₈H₄O₄^-(aq) + OH^-(aq) $\leftrightharpoons$ C₈H₄O₄^2-(aq) + H₂O( $\ell$ )

A) 0.02318 M
B) 0.05705 M
C) 0.0859 M
D) 0.1141 M
E) 0.1429 M

Question 61

If 500 mL of 1.4 × 10^-6 M AgNO₃ is mixed with 500 mL of 1.4 × 10^-6 M NaBr, what will occur? For AgBr, K_sp = 5 × 10^-13.

A) Silver(I) bromide will precipitate.
B) The concentration of Ag⁺ will be 1.4 × 10^-6 M.
C) 7.0 × 10^-7 mol of AgBr will form.
D) No precipitation will occur.
E) Sodium bromide will precipitate.

Question 62

Given the following equilibrium constants, Zn4IO₃)₂ K_sp = $3.9 \times 10 - 6$ Zn(NH₃)₄²⁺ K_f = $2.9 \times 10 ^ { 9 }$ determine K for the dissolution of the sparingly soluble salt Zn(IO₃)₂ in aqueous ammonia (shown below).
Zn(IO₃)₂(s) + 4NH₃(aq) ? Zn(NH₃)₄²⁺(aq) + 2IO₃^-(aq)

A) $1.1 \times 10 ^ { 4 }$
B) $1.3 \times 10 ^ { - 15 }$
C) $7.4 \times 10 ^ { 14 }$
D) $8.8 \times 10 ^ { - 5 }$
E) $2.9 \times 10 ^ { 9 }$

Question 63

What is the minimum mass of Na₂CO₃ (molar mass = 105.990 g/mol) that must be added to 43.4 mL of a 1.0 × 10^-4 M AgNO₃ solution in order for precipitation to occur? The K_sp of Ag₂CO₃ is 8.6 × 10^-12. Assume no volume change occurs upon addition of Na₂CO₃.

A) 4.6 × 10^-4 g
B) 3.1 × 10^-4 g
C) 2.3 × 10^-4 g
D) 4.0 × 10^-7 g
E) 4.0 × 10^-3 g

Question 64

What is the minimum concentration of Cd²⁺ required to begin precipitating Cd(OH)₂(s) in a solution buffered at pH 10.83? The K_sp of Cd(OH)₂ is 5.3 × 10^-15 and K_w = 1.01 × 10^-14.

A) 3.4 × 10^-4 M
B) 3.6 × 10^-4 M
C) 7.8 × 10^-12 M
D) 1.2 × 10^-8 M
E) 4.5 × 10^-17 M

Question 65

Calculate the molar concentration of uncomplexed Zn²⁺(aq) in a solution that contains 0.17 M Zn(NH₃)₄²⁺ and 0.3775 M NH₃ at equilibrium. K_f for Zn(NH₃)₄²⁺ is $2.9 \times 10 ^ { 9 }$ .

A) $2.9 \times 10 ^ { - 9 }$ M
B) $1.6 \times 10 ^ { - 10 }$ M
C) $3.5 \times 10 ^ { 8 }$ M
D) $4.1 \times 10 ^ { - 10 }$ M
E) $2.7 \times 10 ^ { 0 }$ M

Question 66

In which of the following solutions would silver(I) phosphate, Ag₃PO₄, be least soluble?

A) 0.10 M Na₃PO₄
B) 0.10 M AgNO₃
C) 0.10 M Na₂HPO₄
D) 0.10 M HNO₃
E) 0.10 M NaH₂PO₄

Question 67

Consider the reaction
Cu²⁺(aq) + 4 NH₃(aq) $\leftrightharpoons$ Cu(NH₃)₄²⁺(aq)
K_f = 2.1 × 10¹³
If the K_sp for Cu(OH)₂ is 2.2 × 10^-20, what is the value of the equilibrium constant, K, for the reaction below?
Cu(NH₃)₄²⁺(aq) + 2 OH^-(aq) $\leftrightharpoons$ Cu(OH)₂(s) + 4 NH₃(aq)

A) 1.0 × 10^-33
B) 4.6 × 10^-7
C) 2.1 × 10¹³
D) 2.2 × 10⁶
E) 9.5 × 10³²

Question 68

An aqueous solution contains 0.010 M bromide ion (Br^-) and 0.010 M iodide ion (I^-). If silver ions (Ag⁺) are added to the solution until silver bromide just begins to precipitate, what are the concentrations of silver ions and iodide ions? (K_sp of AgBr = 5.4 × 10^-13 and K_sp of AgI = 8.5 × 10^-17)

A) [Ag⁺] = 5.4 × 10^-11 M, [I^-] = 1.0 × 10^-2 M
B) [Ag⁺] = 8.5 × 10^-15 M, [I^-] = 1.0 × 10^-2 M
C) [Ag⁺] = 5.4 × 10^-11 M, [I^-] = 1.6 × 10^-6 M
D) [Ag⁺] = 8.5 × 10^-15 M, [I^-] = 6.4 × 10¹ M
E) [Ag⁺] = 8.5 × 10^-15 M, [I^-] = 1.6 × 10^-6 M

Question 69

Two important biological buffer systems control pH in the range of 6.9 to 7.4. These buffer systems are H₂CO₃/HCO₃^- and _____.

Question 70

The following anions can be separated by precipitation as silver salts: Cl^-, Br^-, I^-, and CrO₄^2-. If silver ions (Ag⁺) are added to a solution containing the four anions that are at concentrations of 0.10 M, in what order will they precipitate? $$\begin{array} { l l } \text { Compound } & K _ { \mathrm { sp } } \\\hline \mathrm { AgCl } & 1.8 \times 10 ^ { - 10 } \\\mathrm { Ag } _ { 2 } \mathrm { CrO } _ { 4 } & 1.1 \times 10 ^ { - 12 } \\\mathrm { AgBr } & 5.4 \times 10 ^ { - 13 } \\\mathrm { AgI } & 8.5 \times 10 ^ { - 17 }\end{array}$$

A) AgCl ? Ag₂CrO₄ ? AgBr ? AgI
B) AgI? AgBr ? Ag₂CrO₄ ? AgCl
C) Ag₂CrO₄ ? AgCl ?AgBr ?AgI
D) Ag₂CrO₄ ? AgI ? AgBr ? AgCl
E) AgI ? AgBr ? AgCl ?Ag₂CrO₄

Question 71

What is the maximum hydroxide-ion concentration that a 0.019 M MgCl₂ solution could have without causing the precipitation of Mg(OH)₂? For Mg(OH)₂, K_sp = 1.8 × 10^-11.

A) 4.2 × 10^-6
B) 1.7 × 10^-4
C) 1.2 × 10^-8
D) 9.5 × 10^-9
E) 3.1 × 10^-5

Question 72

Given the two equilibria below,
Ag(NH₃)₂⁺(aq) $\rightleftharpoons$$\leftrightharpoons$ Ag⁺(aq) + 2NH₃(aq); K_d = 5.9 × 10^-8
AgCN(s) $\rightleftharpoons$ Ag⁺(aq) + CN?(aq); K_sp = $2.2 \times 10 ^ { - 16 }$ what is K for the following equilibrium?
AgCN(s) + 2NH₃(aq) $\rightleftharpoons$ Ag(NH₃)₂⁺(aq) + CN^-(aq)

A) $3.7 \times 10 ^ { - 9 }$
B) $1.3 \times 10 ^ { - 23 }$
C) $2.7 \times 10 ^ { 8 }$
D) $1.4 \times 10 ^ { - 17 }$
E) $2.7 \times 10 ^ { 0 }$

Question 73

What is the molar solubility of solid iron(III) hydroxide, Fe(OH)₃, in a solution that is buffered to a pH of 2.50 at 25 °C? The K_sp of Fe(OH)₃ is 6.3 × 10^-38 at 25 °C.

A) 6.9 × 10^-28 mol/L
B) 2.0 × 10^-26 mol/L
C) 1.3 × 10^-13 mol/L
D) 2.0 × 10^-3 mol/L
E) 5.0 × 10² mol/L

Question 74

A 5.0 × 10^-4 M solution of MnSO₄ is gradually made more basic by adding NaOH. At what pH will manganese(II) hydroxide begin to precipitate? The K_sp of Mn(OH)₂ is 2.0 × 10^-13 and K_w = 1.01 × 10^-14.

A) 4.60
B) 9.57
C) 4.70
D) 9.30
E) 9.40

Question 75

Suppose 50.00 mL of 2.0 × 10^-5 M Fe(NO₃)₃ is added to 50.00 mL of 2.0 ×10^-4 M KIO₃. Which of the following statements is true?
For Fe(IO₃)₃, K_sp = 1.0 × 10^-14.

A) A precipitate forms because Q_c > K_sp.
B) A precipitate forms because Q_c < K_sp.
C) No precipitate forms because Q_c < K_sp.
D) No precipitate forms because Q_c = K_sp.
E) No precipitate forms because Q_c > K_sp.

Question 76

What is the molar solubility of Mn(OH)₂(s) in a solution that is buffered at pH 8.00 at 25 °C? The K_sp of Mn(OH)₂ is 1.9 × 10^-13 at 25 °C.

A) 3.6 × 10^-8 mol/L
B) 1.9 × 10^-7 mol/L
C) 3.6 × 10^-5 mol/L
D) 1.9 × 10^-1 mol/L
E) 1.9 × 10³ mol/L

Question 77

What is the value of the dissociation constant, K_dissociation, for the complex ion Zn(NH₃)₄²⁺? (K_f = 2.9 × 10⁹)

A) 2.9 × 10^-5
B) 7.3 × 10⁸
C) 2.9 × 10⁹
D) 2.3 × 10²
E) 3.4 × 10^-10

Question 78

Given the following reactions,
AgBr(s) $\leftrightharpoons$ Ag⁺(aq) + Br^-(aq)
K_sp = 5.4 × 10^-13
Ag⁺(aq) + 2 CN^-(aq) $\leftrightharpoons$ Ag(CN)₂^-(aq)
K_f = 1.2 × 10²¹
Determine the equilibrium constant for the reaction below.
AgBr(s) + 2 CN^-(aq) $\leftrightharpoons$ Ag(CN)₂^-(aq) + Br^-(aq)

A) 4.5 × 10^-34
B) 1.5 × 10^-9
C) 6.5 × 10⁸
D) 1.2 × 10²¹
E) 2.2 × 10³³

Question 79

The concentration of Pb²⁺ in an aqueous solution is 5.5 × 10^-3 M. What concentration of SO₄^2- is required to begin precipitating PbSO₄? The K_sp of PbSO₄ is 2.5 × 10^-8.

A) 1.4 × 10^-10 M
B) 4.5 × 10^-6 M
C) 1.6 × 10^-4 M
D) 8.3 × 10^-4 M
E) 2.9 × 10^-2 M

Question 80

What is the concentration of Cd²⁺(aq) in a mixture of 0.014 mol Cd(NO₃)₂ and 1.0 mol NH₃ diluted to 1.00 L? For Cd(NH₃)₄²⁺, K_f = 1.0 × 10⁷.​

A) 3.7 × 10^-5 M
B) ​​1.5 × 10^-9 M
C) 1.8 × 10^-9 M
D) 3.2 × 10^-4 M
E) ​​1.4 × 10^-2 M