Unit 4-1 Provincial Practice Questions Page 1

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9 55. The conjugate base of HAsO 4 2 is A. H 3 O + B. 3 AsO 4 C. H 3 AsO 4 D. H 2 AsO Consider the following acidbase equilibrium: HC 6 H 5 O H 2 PO 4 H 2 C 6 H 5 O 7 + HPO 4 2 In the equilibrium above, A. products are favoured because H 2 PO 4 is the weaker acid B. reactants are favoured because HPO 4 2 is the weaker acid C. products are favoured because HC 6 H 5 O 7 2 is the weaker acid D. reactants are favoured because HC 6 H 5 O 7 2 is the weaker base 57. Calculate the [H 3 O + ] in a M solution of Sr(OH) 2. A. 5.0 x M B. 1.0 x M C. 1.0 x 10 2 M D. 2.0 x 10 2 M 58. The conjugate acid of H 2 PO 4 is A. 3 PO 4 B. HPO 4 C. 2 HPO 4 D. H 3 PO The electrical conductivities of 0.010M solutions of NaCl, HCN and HNO 2 are measured. The order by conductivity from highest to lowest is A. NaCl > HNO 2 > HCN B. HCN > HNO 2 > NaCl C. NaCl > HCN l > HNO 2 D. HNO 2 > HCN > NaCl Page 9

10 60. Which of the following acids has the weakest conjugate base? A. H 2 C 2 O 4 B. HF C. H 3 PO 4 D. HCN 61. Which of the following represents the reaction of H 2 PO 4 acting as a base? A. H 2 PO 4 B. H 2 PO 4 C. H 2 PO 4 D. H 2 PO 4 + H 2 O H 3 PO 4 + OH + H 2 O H 3 O + + H 3 PO 4 + H 2 O H 3 O HPO 4 + 2H 2 O H 4 PO OH 62. An acidic solution can be defined as one in which A. [H 3 O + ] is not present B. [H 3 O + ] is equal to [OH ] C. [H 3 O + ] is less than [OH ] D. [H 3 O + ] is greater than [OH ] 63. What is [OH ] in M HNO 3? A. 4.0 x M B M C M D M 64. Which of the following relationships is used to calculate Kw at 30 o C? A. Kw = ph + poh B. pkw = log[h 3 O + ] C. Kw = [H 3 O + ] [OH ] D. Kw = [H 3 O + ] + [OH ] 65. Which of the following Kb values represents the base with the strongest conjugate acid? A. Kb = 4.2 x B. Kb = 9.5 x 10 5 C. Kb = 2.0 x 10 3 D. Kb = 7.8 x 10 2 Page 10

11 66. Consider the ionization of water: 2 H 2 O (l) H 3 O + (aq) + OH (aq) What happens to the ph when 0.1M HNO 3 is added to water? A. ph increases and [OH ] increases. B. ph increases and [OH ] decreases. C. ph decreases and [OH ] increases. D. ph decreases and [OH ] decreases. E. ph remains the same 67. Since the ionization of water is endothermic, which of the following is true at 12 o C? A. B. Kw = Kw = Ka Kb Kb Ka C. Kw > 1.0 x D. Kw < 1.0 x When 10.0 ml of 0.10M HCl is added to 10.0 ml of water, the concentration of OH in the final solution is A M B M C. 1.0 x M D. 2.0 x M 69. Which of the following chemical species are amphiprotic in aqueous solution? I. 2 C 2 O 4 II. HS III. H 2 PO 4 A. I only B. II only C. III only D. II and III only Page 11

12 70. Consider the following equilibrium: 2H 2 O (l) + energy H 3 O + (aq) + OH (aq) The [H 3 O + ] and the [OH ] will both decrease when A. a strong acid is added B. a strong base is added C. the temperature is increased D. the temperature is decreased 71. A BronstedLowry base is defined as a compound that A. accepts OH in solution. B. releases OH in solution. C. accepts protons in solution. D. donates protons in solution. 72. Consider the equilibrium: HF (aq) + HPO 4 2 (aq) F (aq) + H 2 PO 4 (aq) For the above equilibrium, identify the stronger acid and determine whether reactants or products are favoured. Weaker Acid Side Favoured A. HF Products B. HF Reactants C. H 2 PO 4 Products D. H 2 PO 4 Reactants 73. Which of the following will have the largest Kb value? A. IO 3 B. NH 3 C. CN D. 2 HPO 4 Page 12

13 74. Four acids are analyzed and their Ka values are determined. Which of the following values represents the weakest acid? A. Ka = 2.2 x 10 2 B. Ka = 6.2 x 10 9 C. Ka = 1.7 x D. Ka = 1.2 x Which of the following is generally true of bases, but not for acids? A. ph < 7 B. feel slippery C. conduct current when in solution D. cause indicators to change colour 76. Identify the common acid used for etching copper. A. nitric acid B. sulphuric acid C. perchloric acid D. hydrochloric acid 77. Consider the following equilibrium: HCO 3 + H 2 PO 4 HPO H 2 CO 3 What are the BronstedLowry bases in this equilibrium? A. HCO 3 and H 2 CO 3 B. HCO 2 3 and HPO 4 C. H 2 PO 4 and H 2 CO 3 D. H 2 PO 2 4 and HPO What happens to the ion concentrations in water when a small amount of KOH (aq) is added? A. [H 3 O + ] = [OH ] = 1.0 x 10 7 M B. [H 3 O + ] and [OH ] both increase C. [H 3 O + ] decreases and [OH ] increases D. [H 3 O + ] increases and [OH ] is unchanged Page 13

14 Chemistry 12 Provincial Practice Questions Written Response Questions 1. Consider the following amphiprotic anions reacting with each other: H 2 C 6 H 5 O 7 + H 2 PO 4? a) Complete the BronstedLowry acidbase equilibrium for the predominant reaction. Write your answer here: b) Does the equilibrium above favour reactants or products? c) Explain your answer to (b). 2. Calculate the ph of a 2.5 M C 6 H 5 OH solution. Page 14

15 3. Calculate the ph of a 0.60 M NaNO 2 solution. 4. Calculate the ph of 0.45 M Ra(OH) Write the balanced formula equation to represent the complete neutralization reaction between aluminum hydroxide and sulphuric acid. 6. a) Write the net ionic equation for the acidbase reaction that occurs between KF (aq) and NH 4 NO 3(aq). (2 marks) b) Are reactants or products favoured at equilibrium? (1 mark) are favoured. Page 15

16 7. A sample of pure KOH (s) is dissolved in water to make 8.0 L of solution and a ph = 9.82 results. Calculate the mass of pure KOH that was dissolved. (3 marks) 8. At 20 o C, the poh of a sample of water is Calculate the value of Kw for water at 20 o C using this data. 9. a) Which has a higher conductivity, 2.0 M H 2 S or 0.01 M HBr? b) Justify your answer using calculations. Page 16

17 10. At a particular temperature a 1.0 M HCN solution has a ph = Calculate the value of Ka at this temperature. (4 marks) 11. A 0.65 M solution of CN has a ph of at a certain temperature. Calculate the Kb of CN at this temperature. (Assume pka = 14.00) 12. Explain why H 3 O + is the strongest acid possible in aqueous solution. 13. What is the ph of a 0.70 M oxide solution? Page 17

18 14. Write the equation for an amphiprotic anion acting as an acid with water. 15. How much water needs to be added to ml of a solution of ph = to bring the ph to A 0.60 M solution of a weak acid has a ph = Use calculations and the table of acids to identify which acid it is. a) Write an equation to represent the predominant reaction when HC 6 H 5 O 7 2 is mixed with HCO 3. (1 mark) b) Justify your statement by comparing Ka values. (1 mark) c) Identify a conjugate acidbase pair. (1 mark) and d) Predict whether equilibrium will favour the production of reactants or products. Explain. (2 marks) Prediction: Explanation: Page 18