1. Which statement explains why ammonia can act as a Lewis base? A. Ammonia can donate a lone pair of electrons. B. Ammonia can accept a lone pair of electrons. C. Ammonia can donate a proton. D. Ammonia can accept a proton. 2. Consider the equilibrium below. CH 3 CH 2 COOH(aq) + H 2 O(l) CH 3 CH 2 COO (aq) + H 3 O + (aq) Which species represent a conjugate acid-base pair? A. CH 3 CH 2 COOH and H 2 O B. H 2 O and CH 3 CH 2 COO C. H 3 O + and H 2 O D. CH 3 CH 2 COO and H 3 O + 3. Which property is characteristic of acids in aqueous solution? A. Acids react with ammonia solution to produce hydrogen gas and a salt. B. Acids react with metal oxides to produce oxygen gas, a salt and water. C. Acids react with reactive metals to produce hydrogen gas and a salt. D. Acids react with metal carbonates to produce hydrogen gas, a salt and water. IB Questionbank Chemistry 1
4. What is the K b expression for the reaction of ethylamine with water? A. K b = [CH 3 CH 2 NH 3 + ][OH ] B. K b = C. K b = [CH [CH 3 CH [CH 3 3 CH [CH 3 2 NH CH 2 CH 2 NH 2 3 NH 3 NH ][OH 2 ] ][H 2 ] 2 ] O] D. K b = [CH 3 CH 2 NH 2 ][H 2 O] 5. Which statement about acids is correct? A. A Brønsted-Lowry acid donates an electron pair. B. A Lewis acid donates a proton. C. A Brønsted-Lowry acid accepts a proton. D. A Lewis acid accepts an electron pair. 6. Salts may form neutral, acidic or alkaline solutions when dissolved in water. (i) Explain why a solution of sodium chloride is neutral but sodium carbonate forms an alkaline solution when it dissolves in water. (2) IB Questionbank Chemistry 2
(ii) Explain why iron(iii) chloride, [Fe(H 2 O) 6 ]Cl 3, forms an acidic solution in water. (2) (Total 4 marks) 7. A student has equal volumes of 1.0 mol dm 3 sodium hydroxide and ammonia solutions. Which statement about the solutions is correct? A. Sodium hydroxide has a lower electrical conductivity than ammonia. B. Sodium hydroxide has a higher hydrogen ion concentration than ammonia. C. Sodium hydroxide has a higher ph than ammonia. D. Sodium hydroxide has a higher hydroxide ion concentration than ammonia. 8. Define an acid in terms of the Lewis theory. Deduce, giving a reason, whether NF 3 is able to function as a Lewis acid or as a Lewis base............. (Total 2 marks) IB Questionbank Chemistry 3
9. (i) 25.0 cm 3 of 1.00 10 2 mol dm 3 hydrochloric acid solution is added to 50.0 cm 3 of 1.00 10 2 mol dm 3 aqueous ammonia solution. Calculate the concentrations of both ammonia and ammonium ions in the resulting solution and hence determine the ph of the solution. (5) (ii) State what is meant by a buffer solution and explain how the solution in (i), which contains ammonium chloride dissolved in aqueous ammonia, can function as a buffer solution. (3) (Total 8 marks) IB Questionbank Chemistry 4
10. The graph below shows the titration curve of 25 cm 3 of 0.100 mol dm 3 of hydrochloric acid with sodium hydroxide, of 0.100 mol dm 3 concentration. The indicator methyl orange was used to determine the equivalence point. Methyl orange has a ph range of 3.2 4.4. If the hydrochloric acid was replaced by ethanoic acid of the same volume and concentration, which property of the titration would remain the same? A. The initial ph B. The ph at the equivalence point C. The volume of strong base, NaOH, needed to reach the equivalence point D. The colour of the titration mixture just before the equivalence point is reached IB Questionbank Chemistry 5
11. Ammonia, NH 3, is a weak base. It has a pk b value of 4.75. Calculate the ph of a 1.00 10 2 mol dm 3 aqueous solution of ammonia at 298 K......................... (Total 4 marks) 12. Define the terms acid and base according to the Brønsted-Lowry theory and state one example of a weak acid and one example of a strong base............. (Total 2 marks) IB Questionbank Chemistry 6
D. HD 1 10 5 13. Which combination will form a buffer solution? A. 100 cm 3 of 0.10 mol dm 3 hydrochloric acid with 50 cm 3 of 0.10 mol dm 3 sodium hydroxide. B. 100 cm 3 of 0.10 mol dm 3 ethanoic acid with 50 cm 3 of 0.10 mol dm 3 sodium hydroxide. C. 50 cm 3 of 0.10 mol dm 3 hydrochloric acid with 100 cm 3 of 0.10 mol dm 3 sodium hydroxide. D. 50 cm 3 of 0.10 mol dm 3 ethanoic acid with 100 cm 3 of 0.10 mol dm 3 sodium hydroxide. 14. Explain, using the Brønsted-Lowry theory, how water can act either as an acid or a base. In each case identify the conjugate acid or base formed............. (Total 2 marks) 15. Based on information in the table below, which acid is the strongest? Acid pk a K a A. HA 2.0 B. HB 1 10 3 C. HC 4.0 IB Questionbank Chemistry 7
16. The ph of a solution changes from ph = 2 to ph = 5. What happens to the concentration of the hydrogen ions during this ph change? A. It decreases by a factor of 1000 B. It increases by a factor of 1000 C. It decreases by a factor of 100 D. It increases by a factor of 100 17. Describe two different properties that could be used to distinguish between a 1.00 mol dm 3 solution of a strong monoprotic acid and a 1.00 mol dm 3 solution of a weak monoprotic acid............. (Total 2 marks) 18. Which is not a conjugate acid-base pair? A. HNO 3 and NO 3 B. CH 3 COOH and CH 3 COO C. H 3 O + and OH D. HSO 4 and SO 4 2 IB Questionbank Chemistry 8
19. Which 0.10 mol dm 3 solution would have the highest conductivity? A. HCl B. NH 3 C. CH 3 COOH D. H 2 CO 3 20. The graph below indicates the ph change during the titration of 20.0 cm 3 of 0.100 mol dm 3 of CH 3 COOH(aq) with 0.100 mol dm 3 KOH(aq). From the graph, identify the volume of KOH(aq) and the ph at the equivalence point............. (Total 2 marks) IB Questionbank Chemistry 9
21. Determine the ph of the solution resulting when 100 cm 3 of 0.50 mol dm 3 HCl(aq) is mixed with 200 cm 3 of 0.10 mol dm 3 NaOH(aq)............................... (Total 5 marks) 22. (i) Describe how an indicator works. (3) IB Questionbank Chemistry 10
(ii) Using Table 16 of the Data Booklet, identify the most appropriate indicator for the titration of ethanoic acid with potassium hydroxide. Explain your choice. (2) (Total 5 marks) 23. Explain, using an equation, whether a solution of 0.10 mol dm 3 FeCl 3 (aq) would be acidic, alkaline or neutral............. (Total 2 marks) 24. (i) Define the terms acid and base according to the Brønsted-Lowry theory. Distinguish between a weak base and a strong base. State one example of a weak base. (3) IB Questionbank Chemistry 11
(ii) Weak acids in the environment may cause damage. Identify a weak acid in the environment and outline one of its effects. (2) (Total 5 marks) 25. Describe two different methods, one chemical and one physical, other than measuring the ph, that could be used to distinguish between ethanoic acid and hydrochloric acid solutions of the same concentration......................... (Total 4 marks) IB Questionbank Chemistry 12
26. In an experiment conducted at 25.0 C, the initial concentration of propanoic acid and methanol were 1.6 mol dm 3 and 2.0 mol dm 3 respectively. Once equilibrium was established, a sample of the mixture was removed and analysed. It was found to contain 0.80 mol dm 3 of compound X. (i) Calculate the concentrations of the other three species present at equilibrium. (3) (ii) State the equilibrium constant expression, K c, and calculate the equilibrium constant for this reaction at 25.0 C. (2) (Total 5 marks) 27. The K b value for a base is 5.0 10 2 mol dm 3 at 298 K. What is the K a value for its conjugate acid at this temperature? A. 5.0 10 2 B. 2.0 10 6 C. 2.0 10 12 D. 2.0 10 13 IB Questionbank Chemistry 13
28. Which compounds can be mixed together as solutions of equal volume and concentration to form a buffer solution? A. Nitric acid and potassium hydroxide B. Nitric acid and potassium nitrate C. Propanoic acid and potassium hydroxide D. Propanoic acid and potassium propanoate 29. Black coffee has a ph of 5 and toothpaste has a ph of 8. Identify which is more acidic and deduce how many times the [H + ] is greater in the more acidic product............. (Total 2 marks) 30. Which salts will produce an acidic solution when dissolved in water? I. CH 3 COOK II. NH 4 NO 3 III. Al 2 (SO 4 ) 3 A. I and II only B. I and III only C. II and III only D. I, II and III IB Questionbank Chemistry 14