SCH4U Chapter 8 review

Transcription

1 Name: Class: Date: SCH4U Chapter 8 review Multiple Choice Identify the choice that best completes the statement or answers the question. 1. Which statement does not describe a characteristic of acidic solutions? A) They react with metals to form hydrogen gas. B) They turn phenolphthalein pink. C) They do not react with fatty acids. D) They are made from non-metal oxides. E) They conduct electricity. 2. Which statement does not describe a characteristic of basic solutions? A) They turn litmus paper blue. B) They react with ammonium chloride to produce ammonia gas. C) They react with carbonates to form carbon dioxide gas. D) They feel slippery. E) They taste bitter. 3. What is the Arrhenius definition of an acid? A) a substance that donates protons B) a substance that accepts protons C) a substance that dissolves in water to form OH ions D) a substance that dissolves in water to form H + ions 4. What is the Brønstead-Lowry definition of a base? A) a substance that donates protons B) a substance that accepts protons C) a substance that dissolves in water to form OH ions D) a substance that dissolves in water to form H + ions 5. What is the formula of a hydronium ion? A) H 3 O + (aq) C) H + (aq) D) H 2 O + (aq) E) H 4 O Which compound is a strong acid? A) HClO (aq) B) HIO 3(aq) C) HClO 4(aq) D) HC 2 H 3 O 2(aq) E) NaOH 7. Which compound is not a strong base? A) ammonium hydroxide B) sodium hydroxide C) barium hydroxide D) magnesium hydroxide E) cesium hydroxide 8. Which acid or base is not a good electrolyte? A) H 2 SO 4(aq) B) KOH (aq) C) HBr (aq) D) NH 2 CONH 2(aq) E) All acids and bases are good electrolytes. 1

2 Name: 9. What is the conjugate acid of H 2 PO 4 (aq)? A) H 3 O +(aq) C) H 3 PO 4(aq) D) HPO 2 4 (aq) E) PO 3 4 (aq) 10. What is the conjugate base of HSO 4 (aq)? A) H 3 O + (aq) C) H 2 SO 4(aq) D) SO 2 4 (aq) E) This compound does not have a conjugate base. 11. Which term describes a substance that acts as a proton donor and a proton acceptor? A) amphoteric B) monoprotic C) polyprotic D) buffer E) acid-base 12. What is the most important factor for determining the strength of binary acids across a period in the periodic table? A) strength of the bond B) number of oxygen atoms C) electronegativity D) number of hydrogen atoms E) size of the nucleus 13. Which equation below is incorrect. A) KaKb Kw B) Kw [OH - ][H ] C) Kw [OH - ]+[H ] D) ph-log[h ] E) [H ] 10 -ph 14. Based on your knowledge of the relative strength of oxoacids, which acid is the strongest acid? A) HIO (aq) B) HIO 2(aq) C) HIO 3(aq) D) HIO 4(aq) E) These acids are all the same strength. 15. What is the concentration of hydroxide ions in a solution of mol/l HI (aq)? A) mol/l B) mol/l C) mol/l D) mol/l E) 1.30 mol/l 16. A solution contains hydronium ions. What is the ph of the solution? A) 4.20 B) 5.00 C) 6.30 D) 9.80 E) A solution has a poh of What is the concentration of hydroxide ions in the solution? A) B) C) D)

3 Name: 18. A solution has a ph of What is the concentration of hydroxide ions in the solution? A) B) C) D) Identify the weakest acid. A) HCN K a B) HCOOH K a C) HNO 2 K a D) HF K a E) All acids are the same strength, as long as they have a dissociable hydrogen ion. Short Answer For the following questions, write the most appropriate answer in the space provided. 20. Label the conjugate acid-base pairs in each reaction. a) CO 3 2 (aq) + H 2 O (l) HCO 3 (aq) + OH (aq) b) H 2 SO 4(aq) + H 2 O (l) H 3 O + (aq) + HSO 4 (aq) a) CO 2 3 (aq) + H 2 O (l) HCO 3 (aq) + OH (aq) base 1 acid 2 conjugate acid 1 conjugate base 2 b) H 2 SO 4(aq) + H 2 O (l) H 3 O + (aq) + HSO 4 (aq) acid 1 base 2 conjugate acid 2 conjugate base 1 Problem Critical Thinking For the following questions, write the answer in the space provided. Use complete sentences in your answer. If the question requires mathematical calculations, show all of your work. Write a final statement that gives your solution. 21. A solution of hydrocyanic acid has an initial concentration of mol/l. What are the concentrations of the ions at equilibrium, if K a Concentration (mol/l) HCN (aq) + H 2 O (l) H 3 O + (aq) + CN (aq) Initial Change x x x Final ( ) x x x K a [H 3 O + ][CN ] [HCN] ( ) x Since x is very small, use an approximation x The equilibrium concentrations of H 3 O + (aq) and CN (aq) are mol/l. The equilibrium concentration of HCN (aq) is mol/l. 3

4 Name: 22. Lactic acid, C 3 H 6 O 3, builds up in human muscles during anaerobic exercise. If the initial concentration of lactic acid is 0.12 mol/l and the ph is 2.39, what is K a for lactic acid? How to look at this. The ph is telling you the concentration of the H 3 O + (aq) and C 3 H 5 O 3 (aq) ph log[h 3 O + (aq)] [H 3 O + ] 10 ph mol/l Concentration (mol/l) C 3 H 6 O 3(aq) + H 2 O (l) H 3 O + (aq) + C 3 H 5 O 3 (aq) Initial Change Final K a [H 3 O+ ][C 3 H 5 O 3 ] [C 3 H 6 O 3 ] ( )( ) Therefore, K a is Calculate the ph of a solution of H 2 CO 3, with an initial concentration of mol/l. K a for H 2 CO 3 is , and K a for HCO 3 is Since K a for HCO 3 is so small, the amount of hydrondium ion produced by this step is negligible. Therefore, only the first ionization step needs to be considered when determining the ph of the solution. Concentration (mol/l) H 2 CO 3(aq) + H 2 O (l) H 3 O + (aq) + HCO 3 (aq) Initial Change x x x Final x x x K a [H 3 O + ][HCO 3 ] [H 2 CO 3 ] x Since x is very small, use an approximation x The equilibrium concentration of H 3 O + (aq) is mol/l. ph log[h 3 O + ] log( ) 4.19 The ph of the solution is

5 Name: 24. A 30.0 ml solution of a diprotic acid called oxalic acid, C 2 H 2 O 4, is completely neutralized by titration with 56 ml of a mol/l solution of potassium hydroxide. What is the concentration of the oxalic acid? C 2 H 2 O 4(aq) + 2KOH (aq) 2H 2 O (l) + K 2 C 2 O 4(aq) Moles KOH that was used to V C (0.056 L)(0.050 mol/l) mol Moles C 2 H 2 O 4 Moles KOH 1 molc 2 H 2 O 4 2 mol KOH (note 1 to 2 ratio for acid to base) mol KOH 1 molc 2 H 2 O 4 2 mol KOH mol (could look at it as half the amt of acid will be neutralized or that for every 2 mols of base only 1 mol of acid is neutralized) Concentration C 2 H 2 O 4 Moles C 2 H 2 O 4 Volume C 2 H 2 O mol L mol/l 25. A chemist dissolved some Aspirin in water. The chemist then measured the ph of the solution and found it to be 2.73 at 25C. What are the [H3O+] and [OH.] of the solution? 5