Deck 16: Aqueous Ionic Equilibrium

Question 1

Calculate the pH of a buffer that is 0.158 mol L^-1 HClO and 0.099 mol L^-1 NaClO. The K_a for HClO is 2.9 × 10^-8.

A)7.54
B)6.67
C)3.77
D)6.46
E)7.33

Answer 1

7.33

Question 2

Calculate the pH of a solution formed by mixing 200.0 mL of 0.30 mol L^-1 HClO with 100.0 mL of 0.20 mol L^-1 KClO. The K_a for HClO is 2.9 × 10^-8.

A)5.99
B)8.01
C)7.54
D)7.06
E)6.46

Answer 2

7.06

Question 3

Calculate the pH of a solution formed by mixing 250.0 mL of 0.15 mol L^-1 NH₄Cl with 100.0 mL of 0.20 mol L^-1 NH₃. The K_b for NH₃ is 1.8 × 10^-5.

A)9.13
B)9.25
C)9.53
D)4.74
E)8.98

Answer 3

8.98

Question 4

Which one of the following statements is TRUE?

A)A buffer is an aqueous solution composed of two weak acids.
B)A buffer can absorb an unlimited amount of acid or base.
C)A buffer resists pH change by neutralizing added acids and bases.
D)A buffer does not change pH when large amounts of a strong acid or a strong base are added.
E)The common ion in a buffer solution does not have any effect on the dissociation of the acidic component of the buffer solution.

Question 5

Calculate the pH of a buffer that is 0.020 mol L^-1 HF and 0.040 mol L^-1 LiF. The K_a for HF is 3.5 × 10^-4.

A)2.06
B)4.86
C)3.16
D)3.46
E)3.76

Question 6

If the pK_a of HCOOH is 3.74 and the pH of an HCOOH/HCOONa buffer solution is 3.74, which of the following is TRUE?

A)[HCOOH] > [HCOONa]
B)[HCOOH] = [HCOONa]
C)[HCOOH] < [HCOONa]
D)[HCOOH] << [HCOONa]
E)[HCOOH] >> [HCOONa]

Question 7

You wish to prepare a buffer containing CH₃COOH with a pH of 5.44. If the pK_a of acetic acid is 4.74, what ratio of CH₃COO⁻/CH₃COOH must you use?

A)0.70
B)0.20
C)1.4
D)5.0
E)1.1

Question 8

Calculate the pH of a solution formed by mixing 250.0 mL of 0.15 mol L^-1 NH₄Cl with 200.0 mL of 0.12 mol L^-1 NH₃. The K_b for NH₃ is 1.8 × 10^-5.

A)9.06
B)9.45
C)4.55
D)4.74
E)9.26

Question 9

If the pKa of HCOOH is 3.74 and the pH of an HCOOH/HCOONa solution is 3.11, which of the following is TRUE?

A)[HCOOH] < [HCOONa]
B)[HCOOH] = [HCOONa]
C)[HCOOH] << [HCOONa]
D)[HCOOH] > [HCOONa]
E)[HCOOH] >>> [HCOONa]

Question 10

Identify a good buffer.

A)a solution containing small amounts of both a weak acid and its conjugate base
B)a solution containing significant amounts of both a strong acid and a strong base
C)a solution containing small amounts of both a strong acid and a strong base
D)a solution containing significant amounts of both a weak acid and a strong acid
E)a solution containing significant amounts of both a weak acid and its conjugate base

Question 11

A buffer solution is 0.100 mol L^-1 in both C₆H₅COOH and C₆H₅COOLi and has a pH of 4.19. Which of the following pH values would you expect after the addition of a small amount of a strong base?

A)3.89
B)3.69
C)5.69
D)4.49
E)8.89

Question 12

Calculate the pH of a buffer that is 0.225 mol L^-1 CH₃COOH and 0.162 mol L^-1 CH₃COOK. The K_a for CH₃COOH is 1.8 × 10^-5.

A)4.89
B)9.11
C)4.74
D)9.26
E)4.60

Question 13

Calculate the pH of a buffer that is 0.058 mol L^-1 HF and 0.058 mol L^-1 LiF. The K_a for HF is 3.5 × 10^-4.

A)2.86
B)9.31
C)10.54
D)3.46
E)4.69

Question 14

Calculate the pH of a buffer that is 0.105 mol L^-1 CH₃COOH and 0.146 mol L^-1 CH₃COOK. The K_a for CH₃COOH is 1.8 × 10^-5.

A)4.89
B)9.11
C)4.74
D)9.26
E)4.60

Question 15

Calculate the pH of a solution formed by mixing 100.0 mL of 0.20 mol L^-1 HClO with 200.0 mL of 0.30 mol L^-1 KClO. The K_a for HClO is 2.9 × 10^-8.

A)5.99
B)8.01
C)7.54
D)7.06
E)6.46

Question 16

You wish to prepare a buffer containing CH₃COOH with a pH of 4.24. If the pK_a of acetic acid is 4.74, what ratio of CH₃COO⁻/CH₃COOH must you use?

A)0.10
B)0.50
C)0.32
D)2.0
E)2.8

Question 17

If the pK_a of HCOOH is 3.74 and the pH of an HCOOH/HCOONa buffer solution is 3.89, which of the following is TRUE?

A)[HCOOH] < [HCOONa]
B)[HCOOH] = [HCOONa]
C)[HCOOH] > [HCOONa]
D)[HCOOH] >> [HCOONa]
E)[HCOOH] <<< [HCOONa]

Question 18

Which of the following solutions represents a good buffer system?

A)a solution that is 0.10 mol L^-1 CH₃COOH and 0.10 mol L^-1 CH₃COOLi
B)a solution that is 0.10 mol L^-1 HF and 0.10 mol L^-1 CH₃COONa
C)a solution that is 0.10 mol L^-1 HCl and 0.10 mol L^-1 NH₄⁺
D)a solution that is 0.10 mol L^-1 NaOH and 0.10 mol L^-1 KOH
E)a solution that is 0.10 mol L^-1 HCl and 0.10 mol L^-1 KCl

Question 19

Calculate the pH of a buffer that is 0.040 mol L^-1 HF and 0.020 mol L^-1 LiF. The K_a for HF is 3.5 × 10^-4.

A)2.06
B)4.86
C)3.15
D)3.46
E)3.76

Question 20

Which of the following solutions is a good buffer system?

A)a solution that is 0.10 mol L^-1 NaCl and 0.10 mol L^-1 HCl
B)a solution that is 0.10 mol L^-1 HCN and 0.10 mol L^-1 LiCN
C)a solution that is 0.10 mol L^-1 NaOH and 0.10 mol L^-1 HNO₃
D)a solution that is 0.10 mol L^-1 HNO₃ and 0.10 mol L^-1 KNO₃
E)a solution that is 0.10 mol L^-1 HCN and 0.10 mol L^-1 NaCl

Question 21

A 1.00 L buffer solution is 0.150 mol L^-1 in C₆H₅COOH and 0.250 mol L^-1 in C₆H₅COOLi. Calculate the pH of the solution after the addition of 100.0 mL of 1.00 mol L^-1 HCl. The K_a for HC₇H₅O₂ is 6.5 × 10^-5.

A)4.19
B)5.03
C)4.41
D)3.34
E)3.97

Question 22

Calculate the pH of a solution formed by mixing 250.0 mL of 0.15 mol L^-1 HCOOH with 100.0 mL of 0.20 mol L^-1 HCOOLi. The K_a for HCHO₂ is 1.8 × 10^-4.

A)3.87
B)3.74
C)10.53
D)3.47
E)10.13

Question 23

Calculate the pH of a solution formed by mixing 200.0 mL of 0.30 mol L^-1 HClO with 300.0 mL of 0.20 mol L^-1 KClO. The K_a for HClO is 2.9 × 10^-8.

A)5.99
B)8.01
C)7.54
D)7.06
E)6.46

Question 24

A 1.00 L buffer solution is 0.250 mol L^-1 in HF and 0.250 mol L^-1 in NaF. Calculate the pH of the solution after the addition of 100.0 mL of 1.00 mol L^-1 HCl. The K_a for HF is 3.5 × 10^-4.

A)3.09
B)4.11
C)3.82
D)3.46
E)2.78

Question 25

When titrating a strong monoprotic acid with KOH at 25 °C, the

A)pH will be less than 7 at the equivalence point.
B)pH will be greater than 7 at the equivalence point.
C)titration will require more moles of base than acid to reach the equivalence point.
D)pH will be equal to 7 at the equivalence point.
E)titration will require more moles of acid than base to reach the equivalence point.

Question 26

Which of the following is TRUE?

A)An effective buffer has a [base]/[acid] ratio in the range of 10 - 100.
B)A buffer is most resistant to pH change when [acid] = [conjugate base].
C)An effective buffer has very small absolute concentrations of acid and conjugate base.
D)The capacity of a buffer cannot be exceeded by adding too much strong base. It can only be exceeded by adding too much strong acid.
E)A buffer has the best resistance to pH change when the buffer's pH is significantly lower than the pK_a of the acid used to make the buffer solution.

Question 27

When titrating a weak monoprotic acid with NaOH at 25 °C, the

A)pH will be less than 7 at the equivalence point.
B)pH will be equal to 7 at the equivalence point.
C)pH will be greater than 7 at the equivalence point.
D)titration will require more moles of base than acid to reach the equivalence point.
E)titration will require more moles of acid than base to reach the equivalence point.

Question 28

A 1.00 L buffer solution is 0.250 mol L^-1 in HF and 0.250 mol L^-1 in LiF. Calculate the pH of the solution after the addition of 0.150 moles of solid LiOH. Assume no volume change upon the addition of the base. The K_a for HF is 3.5 × 10^-4.

A)3.46
B)4.06
C)2.85
D)3.63
E)4.24

Question 29

Identify the pH of normal blood.

A)7.0
B)7.2
C)7.4
D)7.6
E)7.8

Question 30

When titrating a monoprotic strong acid with a weak base at 25 °C, the

A)pH will be 7 at the equivalence point.
B)pH will be greater than 7 at the equivalence point.
C)titration will require more moles of base than acid to reach the equivalence point.
D)titration will require more moles of acid than base to reach the equivalence point.
E)pH will be less than 7 at the equivalence point.

Question 31

A 1.0 L buffer solution is 0.050 mol L^-1 CH₃COOH and 0.250 mol L^-1 CH₃COOLi. Which of the following actions will destroy the buffer?

A)adding 0.050 moles of NaOH
B)adding 0.050 moles of HCl
C)adding 0.050 moles of CH₃COOH
D)adding 0.050 moles of CH₃COOLi
E)adding 0.050 moles of NH₄Cl.

Question 32

Which of the following acids (listed with pK_a values)and its conjugate base could form a buffer with a pH of 8.10?

A)HC₇H₅O₂, pK_a = 4.19
B)HF, pK_a = 3.46
C)HClO, pK_a = 7.54
D)HCN, pK_a = 9.31
E)HClO₂, pK_a = 1.96

Question 33

Which of the following acids (listed with K_a values)and their conjugate base would be the best choice to make a buffer with a pH of 2.34?

A)C₆H₅COOH, K_a = 6.5 × 10^-5
B)HF, K_a = 3.5 × 10^-4
C)HClO, K_a = 2.9 × 10^-8
D)HCN, K_a = 4.9 × 10^-10
E)HClO₂, K_a = 1.1 × 10^-2

Question 34

Identify the most commonly used indicator among the following five:

A)alizarin
B)thymol blue
C)crystal violet
D)phenolphthalein
E)alizarin yellow R

Question 35

A 1.0 L buffer solution is 0.250 mol L^-1 CH₃COOH and 0.050 mol L^-1 CH₃COOLi. Which of the following actions will exceed the capacity of the buffer?

A)adding 0.050 moles of CH₃COOLi
B)adding 0.050 moles of CH₃COOH
C)adding 0.050 moles of HCl
D)adding 0.050 moles of NaCl
E)adding 0.050 moles of NH₄Cl

Question 36

Which of the following is TRUE?

A)The equivalence point is where the amount of acid equals the amount of base during any acid-base titration.
B)At the equivalence point, the pH is always 7.
C)An indicator is not pH sensitive.
D)A titration curve is a plot of pH vs. the [base]/[acid] ratio.
E)A titration curve is a plot of pH versus titration time.

Question 37

A 1.50 L buffer solution is 0.250 mol L^-1 in HF and 0.250 mol L^-1 in NaF. Calculate the pH of the solution after the addition of 0.0500 moles of solid NaOH. Assume no volume change upon the addition of the base. The K_a for HF is 3.5 × 10^-4.

A)3.34
B)3.46
C)3.57
D)3.63
E)2.89

Question 38

Calculate the pH of a solution formed by mixing 150.0 mL of 0.10 mol L^-1 C₆H₅COOH with 100.0 mL of 0.30 mol L^-1 C₆H₅COONa. The K_a for C₆H₅COOH is 6.5 × 10^-5.

A)4.19
B)9.69
C)4.49
D)4.31
E)10.51

Question 39

What is the maximum ratio of conjugate base to acid in an effective buffer?

A)2
B)5
C)10
D)20
E)15

Question 40

Define buffer capacity.

A)Buffer capacity is the amount of acid or base that can be added to a buffer without destroying its effectiveness.
B)Buffer capacity is the amount of acid that can be added until all the base in the buffer is consumed.
C)Buffer capacity is the amount of base that can be added until all the acid in the buffer is consumed.
D)Buffer capacity is the amount of acid that can be added until all the acid in the buffer is consumed.
E)Buffer capacity is the amount of base that can be added until all the base in the buffer is consumed.

Question 41

A 100.0 mL sample of 0.10 mol L^-1 Ca(OH)₂ is titrated with 0.10 mol L^-1 HBr. Determine the pH of the solution after the addition of 400.0 mL HBr.

A)1.00
B)1.40
C)1.22
D)1.30
E)2.11

Question 42

A 100.0 mL sample of 0.10 mol L^-1 Ca(OH)₂ is titrated with 0.10 mol L^-1 HBr. Determine the pH of the solution before the addition of any HBr.

A)12.86
B)13.00
C)13.30
D)0.70
E)1.00

Question 43

A 100.0 mL sample of 0.10 mol L^-1 Ca(OH)₂ is titrated with 0.10 mol L^-1 HBr. Determine the pH of the solution after the addition of 100.0 mL HBr.

A)2.00
B)12.00
C)1.30
D)12.70
E)7.00

Question 44

A 100.0 mL sample of 0.10 mol L^-1 NH₃ is titrated with 0.10 mol L^-1 HNO₃. Determine the pH of the solution after the addition of 200.0 mL of HNO₃. The K_b of NH₃ is 1.8 × 10^-5.

A)6.44
B)1.48
C)2.00
D)12.52
E)12.00

Question 45

A 100.0 mL sample of 0.18 mol L^-1 HClO₄ is titrated with 0.27 mol L^-1 NaOH. Determine the pH of the solution after the addition of 100.0 mL of NaOH.

A)13.1
B)12.7
C)1.3
D)0.9
E)12.9

Question 46

Identify the indicator that can be used at the lowest pH.

A)alizarin
B)thymol blue
C)crystal violet
D)phenolphthalein
E)alizarin yellow R

Question 47

Identify the indicator that has two endpoints.

A)phenol red
B)thymol blue
C)crystal violet
D)phenolphthalein
E)alizarin yellow R

Question 48

A 100.0 mL sample of 0.10 mol L^-1 NH₃ is titrated with 0.10 mol L^-1 HNO₃. Determine the pH of the solution after the addition of 150.0 mL of HNO₃. The K_b of NH₃ is 1.8 × 10^-5.

A)1.7
B)6.4
C)7.6
D)12.3
E)2.3

Question 49

A 100.0 mL sample of 0.18 mol L^-1 HClO₄ is titrated with 0.27 mol L^-1 NaOH. Determine the pH of the solution after the addition of 30.0 mL of NaOH.

A)0.86
B)1.21
C)2.00
D)1.12
E)2.86

Question 50

A 100.0 mL sample of 0.10 mol L^-1 Ca(OH)₂ is titrated with 0.10 mol L^-1 HBr. Determine the pH of the solution after the addition of 300.0 mL HBr.

A)1.60
B)1.30
C)1.00
D)12.40
E)1.12

Question 51

A 100.0 mL sample of 0.180 mol L^-1 HClO₄ is titrated with 0.270 mol L^-1 NaOH. Determine the pH of the solution after the addition of 75.0 mL of NaOH.

A)12.1
B)2.65
C)11.35
D)1.89
E)13.06

Question 52

A 100.0 mL sample of 0.10 mol L^-1 NH₃ is titrated with 0.10 mol L^-1 HNO₃. Determine the pH of the solution before the addition of any HNO₃. The K_b of NH₃ is 1.8 × 10^-5.

A)4.74
B)9.26
C)11.13
D)13.00
E)12.55

Question 53

A 100.0 mL sample of 0.10 mol L^-1 Ca(OH)₂ is titrated with 0.10 mol L^-1 HBr. Determine the pH of the solution after the addition of 200.0 mL HBr.

A)2.62
B)2.00
C)1.48
D)12.52
E)7.00

Question 54

A 100.0 mL sample of 0.20 mol L^-1 HF is titrated with 0.10 mol L^-1 KOH. Determine the pH of the solution after the addition of 100.0 mL of KOH. The K_a of HF is 3.5 × 10^-4.

A)2.08
B)3.15
C)4.33
D)3.46
E)4.15

Question 55

A 100.0 mL sample of 0.20 mol L^-1 HF is titrated with 0.10 mol L^-1 KOH. Determine the pH of the solution before the addition of any KOH. The K_a of HF is 3.5 × 10^-4.

A)4.15
B)0.70
C)2.08
D)3.46
E)1.00

Question 56

What is the pH of a solution made by mixing 40.00 mL of 0.100 mol L^-1 HCl with 25.00 mL of 0.100 mol L^-1 KOH? Assume that the volumes of the solutions are additive.

A)0.64
B)1.64
C)12.36
D)13.36
E)10.00

Question 57

A 100.0 mL sample of 0.10 mol L^-1 NH₃ is titrated with 0.10 mol L^-1 HNO₃. Determine the pH of the solution after the addition of 50.0 mL of HNO₃. The K_b of NH₃ is 1.8 × 10^-5.

A)4.74
B)7.78
C)7.05
D)9.26
E)10.34

Question 58

A 100.0 mL sample of 0.18 mol L^-1 HClO₄ is titrated with 0.27 mol L^-1 NaOH. Determine the pH of the solution after the addition of 66.67 mL of NaOH (this is the equivalence point).

A)0.97
B)13.03
C)2.76
D)11.24
E)7.00

Question 59

A 100.0 mL sample of 0.18 mol L^-1 HClO₄ is titrated with 0.27 mol L^-1 NaOH. Determine the pH of the solution before the addition of any NaOH.

A)1.74
B)1.05
C)0.74
D)0.57
E)1.57

Question 60

Identify the indicator that can be used at the highest pH.

A)alizarin
B)thymol blue
C)crystal violet
D)phenolphthalein
E)alizarin yellow R

Question 61

Identify the salts that are in hard water.

A)CaCO₃ and MgCO₃
B)MgSO₄ and CaSO₄
C)NaCl and KBr
D)NaHSO₄ and Na₂SO₄
E)NaOCl and HOCl

Question 62

Determine the molar solubility of CaSO₄ in a solution containing 0.100 mol L^-1 Na₂SO₄. K_sp (CaSO₄)= 2.4 × 10^-5.

A)4.9 × 10^-3 mol L^-1
B)2.4 × 10^-4 mol L^-1
C)5.8 × 10^-10 mol L^-1
D)1.2 × 10^-5 mol L^-1
E)0.10 mol L^-1

Question 63

A 100.0 mL sample of 0.20 mol L^-1 HF is titrated with 0.10 mol L^-1 KOH. Determine the pH of the solution after the addition of 200.0 mL of KOH. The K_a of HF is 3.5 × 10^-4.

A)9.62
B)7.00
C)3.46
D)10.54
E)8.14

Question 64

Which of the following compounds' solubility will not be affected by a low pH in solution?

A)AgCl
B)Mg(OH)₂
C)CaF₂
D)CuS
E)BaCO₃

Question 65

Determine the molar solubility of PbSO₄ in pure water. K_sp (PbSO₄)= 1.82 × 10^-8.

A)1.82 × 10^-8 mol L^-1
B)1.35 × 10^-4 mol L^-1
C)9.10 × 10^-9 mol L^-1
D)3.31 × 10^-16 mol L^-1
E)4.48 × 10^-4 mol L^-1

Question 66

Determine the molar solubility of AgBr in a solution containing 0.150 mol L^-1 NaBr. K_sp (AgBr)= 7.7 × 10^-13.

A)8.8 × 10^-7 mol L^-1
B)3.9 × 10^-13 mol L^-1
C)5.8 × 10^-5 mol L^-1
D)5.1 × 10^-12 mol L^-1
E)0.150 mol L^-1

Question 67

The molar solubility of ZnS is 1.6 × 10^-12 mol L^-1 in pure water. Calculate the K_sp for ZnS.

A)8.0 × 10^-13
B)3.2 × 10^-12
C)1.6 × 10^-35
D)2.6 × 10^-24
E)6.8 × 10^-5

Question 68

Identify the expression for the solubility product constant for Cr₂(CO₃)₃.

A)[Cr³⁺]²[CO₃^2-]³
B)
C)
D)
E)[Cr³⁺]³[CO₃^2-]²

Question 69

Identify the expression for the solubility product constant for PbCl₂.

A)
B)
C)[Pb²⁺][Cl⁻]²
D)
E)[Pb²⁺]²[Cl⁻]

Question 70

Which of the following compounds will be more soluble in acidic solution than in pure water?

A)PbCl₂
B)FeS
C)Ca(ClO₄)₂
D)CuI
E)AgBr

Question 71

A 100.0 mL sample of 0.20 mol L^-1 HF is titrated with 0.10 mol L^-1 KOH. Determine the pH of the solution after the addition of 300.0 mL of KOH. The K_a of HF is 3.5 × 10^-4.

A)12.40
B)9.33
C)5.06
D)8.94
E)12.00

Question 72

A 100.0 mL sample of 0.10 mol L^-1 NH₃ is titrated with 0.10 mol L^-1 HNO₃. Determine the pH of the solution after the addition of 100.0 mL of HNO₃. The K_b of NH₃ is 1.8 × 10^-5.

A)6.58
B)10.56
C)8.72
D)3.44
E)5.28

Question 73

Which of the following compounds will have the highest molar solubility in pure water?

A)PbSO₄, K_sp = 1.82 × 10^-8
B)MgCO₃, K_sp = 6.82 × 10^-6
C)AgI, K_sp = 8.51 × 10^-17
D)PbS, K_sp = 9.04 × 10^-29
E)FeS, K_sp = 3.72 × 10^-19

Question 74

Determine the molar solubility of CuCl in a solution containing 0.050 mol L^-1 KCl. K_sp (CuCl)= 1.0 × 10^-6.

A)1.0 × 10^-12 mol L^-1
B)5.0 × 10^-7 mol L^-1
C)2.0 × 10^-5 mol L^-1
D)1.0 × 10^-3 mol L^-1
E)0.050 mol L^-1

Question 75

Which of the following compounds will have the highest molar solubility in pure water?

A)PbS, K_sp = 9.04 × 10^-29
B)CuS, K_sp = 1.27 × 10^-36
C)Al(OH)₃, K_sp = 3 × 10^-34
D)ZnS, K_sp = 1.6 × 10^-24
E)Ag₂S, K_sp = 8 × 10^-48

Question 76

Determine the molar solubility of AgI in pure water. K_sp (AgI)= 8.51 × 10^-17.

A)9.22 × 10^-9 mol L^-1
B)4.26 × 10^-17 mol L^-1
C)8.51 × 10^-17 mol L^-1
D)2.77 × 10^-6 mol L^-1
E)4.40 × 10^-6 mol L^-1

Question 77

Identify the expression for the solubility product constant for BaF₂.

A)
B)
C)[Ba²⁺]²[F⁻]
D)[Ba²⁺][F⁻]²
E)[Ba²⁺][F⁻]

Question 78

A 100.0 mL sample of 0.20 mol L^-1 HF is titrated with 0.10 mol L^-1 KOH. Determine the pH of the solution after the addition of 400.0 mL of KOH. The K_a of HF is 3.5 × 10^-4.

A)13.08
B)12.60
C)13.85
D)12.30
E)12.78

Question 79

Identify the expression for the solubility product constant for Ca₃(PO₄)₂.

A)
B)
C)
D)[Ca²⁺]²[PO₄^3-]³
E)[Ca²⁺]³[PO₄^3-]²

Question 80

Determine the molar solubility of MgCO₃ in pure water. K_sp (MgCO₃)= 6.82 × 10^-6.

A)6.82 × 10^-6 mol L^-1
B)3.41 × 10^-6 mol L^-1
C)4.65 × 10^-3 mol L^-1
D)2.61 × 10^-3 mol L^-1
E)3.25 × 10^-4 mol L^-1