Aqueous Ionic Equilibrium Clicker Questions Chapter 16 Aqueous Ionic Equilibrium Allison Soult University of Kentucky

[H3O+] will increase significantly. What change will be caused by the addition of a small amount of HCl to a HF/NaF buffer? [H3O+] will increase significantly. [F–] and [H3O+] will both increase. [HF] will decrease and [F–] will increase. [F–] will decrease and [HF] will increase. The fluoride ions will precipitate out of solution as its acid salt. Answer: d

[H3O+] will increase significantly. What change will be caused by the addition of a small amount of HCl to a HF/NaF buffer? [H3O+] will increase significantly. [F–] and [H3O+] will both increase. [HF] will decrease and [F–] will increase. [F–] will decrease and [HF] will increase. The fluoride ions will precipitate out of solution as its acid salt. Answer: d

Calculate the pH of a buffer which contains 0 Calculate the pH of a buffer which contains 0.0500 M pyruvic acid and 0.0450 M sodium pyruvate. (The Ka of pyruvic acid is 4.1 × 10–3) 2.34 1.35 1.30 2.41 Answer: d

Calculate the pH of a buffer which contains 0 Calculate the pH of a buffer which contains 0.0500 M pyruvic acid and 0.0450 M sodium pyruvate. (The Ka of pyruvic acid is 4.1 × 10–3) 2.34 1.35 1.30 2.41 Answer: d

What mass of ammonium chloride must be added to a 0 What mass of ammonium chloride must be added to a 0.500 L solution of 0.250 M ammonia to make a buffer with a pH of 9.26? Kb (NH3) = 1.8 × 10–5? 0.12 g 6.6 g 1.4 g 0.028 g Answer: b

What mass of ammonium chloride must be added to a 0 What mass of ammonium chloride must be added to a 0.500 L solution of 0.250 M ammonia to make a buffer with a pH of 9.26? Kb (NH3) = 1.8 × 10–5? 0.12 g 6.6 g 1.4 g 0.028 g Answer: b

Which of the following is true? An effective buffer has a [base]/[acid] ratio in the range of 10 – 100. A buffer is most resistant to pH change when [acid] = [conjugate base]. An effective buffer should have a very small absolute concentration of acid and conjugate base. A buffer cannot be destroyed by adding too much strong base. It can only be destroyed by adding too much strong acid. None of the above are true. Answer: b

Which of the following is true? An effective buffer has a [base]/[acid] ratio in the range of 10 – 100. A buffer is most resistant to pH change when [acid] = [conjugate base]. An effective buffer should have a very small absolute concentration of acid and conjugate base. A buffer cannot be destroyed by adding too much strong base. It can only be destroyed by adding too much strong acid. None of the above are true. Answer: b

None of the above will destroy the buffer. A 1.0 L buffer solution is 0.050 M HC2H3O2 and 0.250 M NaC2H3O2. Which of the following actions will destroy the buffer? adding 0.050 moles of NaC2H3O2 adding 0.050 moles of HC2H3O2 adding 0.050 moles of HCl adding 0.050 moles of NaOH None of the above will destroy the buffer. Answer: d

None of the above will destroy the buffer. A 1.0 L buffer solution is 0.050 M HC2H3O2 and 0.250 M NaC2H3O2. Which of the following actions will destroy the buffer? adding 0.050 moles of NaC2H3O2 adding 0.050 moles of HC2H3O2 adding 0.050 moles of HCl adding 0.050 moles of NaOH None of the above will destroy the buffer. Answer: d

[HCHO2] >> [NaCHO2] [HCHO2] > [NaCHO2] [HCHO2] = [NaCHO2] If the pKa of HCHO2 is 3.74 and the pH of an HCHO2/NaCHO2 solution is 3.89, which of the following is true? [HCHO2] >> [NaCHO2] [HCHO2] > [NaCHO2] [HCHO2] = [NaCHO2] [HCHO2] < [NaCHO2] It is not possible to make a buffer at this pH with these components. Answer: d

[HCHO2] >> [NaCHO2] [HCHO2] > [NaCHO2] [HCHO2] = [NaCHO2] If the pKa of HCHO2 is 3.74 and the pH of an HCHO2/NaCHO2 solution is 3.89, which of the following is true? [HCHO2] >> [NaCHO2] [HCHO2] > [NaCHO2] [HCHO2] = [NaCHO2] [HCHO2] < [NaCHO2] It is not possible to make a buffer at this pH with these components. Answer: d

Which of the following acids and their conjugate base would be the best to form a buffer with a pH of 4.4? HC7H5O2, Ka = 6.5 × 10–5 HF, Ka = 3.5 × 10–4 HClO, Ka = 2.9 × 10–8 HCN, Ka = 4.9 × 10–10 HClO2, Ka = 1.1 × 10–2 Answer: a

Which of the following acids and their conjugate base would be the best to form a buffer with a pH of 4.4? HC7H5O2, Ka = 6.5 × 10–5 HF, Ka = 3.5 × 10–4 HClO, Ka = 2.9 × 10–8 HCN, Ka = 4.9 × 10–10 HClO2, Ka = 1.1 × 10–2 Answer: a

Hypochlorous acid (HOCl) is a weak acid with pKa = 7. 54. Suppose a 45 Hypochlorous acid (HOCl) is a weak acid with pKa = 7.54. Suppose a 45.00 mL sample of 0.240 M HOCl solution is titrated with a 0.250 M standard KOH solution. What is the pH at the equivalence point? 4.15 3.61 9.85 7.41 10.31 Answer: e

Hypochlorous acid (HClO) is a weak acid with pKa = 7. 54. Suppose a 45 Hypochlorous acid (HClO) is a weak acid with pKa = 7.54. Suppose a 45.00 mL sample of 0.240 M HClO solution is titrated with a 0.250 M standard KOH solution. What is the pH at the equivalence point? 4.15 3.61 9.85 7.41 10.31 Answer: e

Which titration curve is reasonable for the titration of a weak acid with a strong base? Answer: d c) d)

Which titration curve is reasonable for the titration of a weak acid with a strong base? Answer: d c) d)

Bromocresol purple (pH range = 5.2 – 6.8) Ephedrine, a weak base, is the active ingredient in many commercial decongestants. A sample is dissolved in 0.200 L of water and titrated to the endpoint with 12.00 mL of 0.900 M HCl. ephedrine, pKb = 4.04 Bromocresol purple (pH range = 5.2 – 6.8) Napthyl red (pH range = 3.7 – 5.0) Thymol blue (pH range = 1.2 – 2.8) Phenolphthalein (pH range = 8.0 – 10.0) None of the above Answer: a

Bromocresol purple (pH range = 5.2 – 6.8) Ephedrine, a weak base, is the active ingredient in many commercial decongestants. A sample is dissolved in 0.200 L of water and titrated to the endpoint with 12.00 mL of 0.900 M HCl. ephedrine, pKb = 4.04 Bromocresol purple (pH range = 5.2 – 6.8) Napthyl red (pH range = 3.7 – 5.0) Thymol blue (pH range = 1.2 – 2.8) Phenolphthalein (pH range = 8.0 – 10.0) None of the above Answer: a

What is the molar solubility of AgCl? Ksp = 1.77×10–10. Answer: b

What is the molar solubility of AgCl? Ksp = 1.77×10–10. Answer: b

Ca5(PO4)3OH (s) 5 Ca2+ (aq) + 3 PO43– (aq) + OH– (aq) Hydroxyapatite is the main mineral component of bone. How many grams of hydroxyapatite will dissolve in 1.00 L of H2O? Ksp = 2.34 × 10–59; Molar mass = 502.3 g/mol? Ca5(PO4)3OH (s) 5 Ca2+ (aq) + 3 PO43– (aq) + OH– (aq) 4.35 × 10–5 g 8.67 × 10–8 g 1.16 × 10–20 g 5.83 × 10–18 g 1.18 × 10–56 g Answer: a

Ca5(PO4)3OH (s) 5 Ca2+ (aq) + 3 PO43– (aq) + OH– (aq) Hydroxyapatite is the main mineral component of bone. How many grams of hydroxyapatite will dissolve in 1.00 L of H2O? Ksp = 2.34 × 10–59; Molar mass = 502.3 g/mol? Ca5(PO4)3OH (s) 5 Ca2+ (aq) + 3 PO43– (aq) + OH– (aq) 4.35 × 10–5 g 8.67 × 10–8 g 1.16 × 10–20 g 5.83 × 10–18 g 1.18 × 10–56 g Answer: a

Which of the following substances will affect the solubility of PbCl2 in aqueous solution? Pb(NO3)2 NaCl KF None of the above Both a and b Answer: e

Which of the following substances will affect the solubility of PbCl2 in aqueous solution? Pb(NO3)2 NaCl KF None of the above Both a and b Answer: e

Which of the following substances will be more soluble in the presence of HCl? NaCl AgCl Ca(OH)2 KBr Answer: c

Which of the following substances will be more soluble in the presence of HCl? NaCl AgCl Ca(OH)2 KBr Answer: c

Ksp (AgCl) = 1.77 × 10−10 Ksp (NaNO3) > 1 A 0.10 M solution of AgNO3 and a solution of 0.075 M NaCl are mixed. What happens? Ksp (AgCl) = 1.77 × 10−10 Ksp (NaNO3) > 1 Sodium nitrate will precipitate out of solution, leaving AgCl in solution. Nothing will happen since NaCl and AgNO3 are both soluble compounds. Silver chloride will precipitate out of solution, leaving a saturated solution of AgCl. Silver chloride will precipitate out of solution, leaving an unsaturated solution of AgCl. Nothing happens since the molar solubility of AgCl is higher than the solution concentration. Answer: c

Ksp (AgCl) = 1.77 × 10−10 Ksp (NaNO3) > 1 A 0.10 M solution of AgNO3 and a solution of 0.075 M NaCl are mixed. What happens? Ksp (AgCl) = 1.77 × 10−10 Ksp (NaNO3) > 1 Sodium nitrate will precipitate out of solution, leaving AgCl in solution. Nothing will happen since NaCl and AgNO3 are both soluble compounds. Silver chloride will precipitate out of solution, leaving a saturated solution of AgCl. Silver chloride will precipitate out of solution, leaving an unsaturated solution of AgCl. Nothing happens since the molar solubility of AgCl is higher than the solution concentration. Answer: c

What concentration of Ag+ remains in a solution that has [Ag+] = 3 What concentration of Ag+ remains in a solution that has [Ag+] = 3.1 × 10–5 M and [CN−] = 0.10 M? Kf of Ag(CN)2− = 1.0 × 1021 0 M 3.1 × 10–24 M 3.1 × 10–5 M 3.1 × 10–25 M Answer: b

What concentration of Ag+ remains in a solution that has [Ag+] = 3 What concentration of Ag+ remains in a solution that has [Ag+] = 3.1 × 10–5 M and [CN−] = 0.10 M? Kf of Ag(CN)2− = 1.0 × 1021 0 M 3.1 × 10–24 M 3.1 × 10–5 M 3.1 × 10–25 M Answer: b