17. A 0.200 mol/L benzoic acid solution has a pH of 1.84 at 25C. What is the percent ionization of benzoic acid at this temperature? a) 3.8% b) 7.2% c) 4.3% d) 5.1% e) 6.6% - 18. Enthalpy changes of reaction are provided for the following reactions. 2C(s) + 2H2(g) C2H4(8) AH = +52 kJ mol-1 2C(s) + 3H2(g) C2H6(g) AH = -85 kJ mol-! What is the enthalpy change, in kJ mol-', for the reaction between ethene and hydrogen? C2H4(g) + H2(g) C2H6(g) a) -137 b) -33 c) +33 d) +137 19. How does the (H) in an aqueous solution with pH = 4 compare with the (H') in a solution with pH = 2? The (H) is a) twice as great b) half as much I LOVE c) 1/10 of the value d) 1/100 of the value CHEMISTI 20. Which is a buffer solution? DOLORE 1. 0.01 mol dm- HCI, 0.01 mol dm- NaCl II. 0.01 mol dm-HNO2, 0.01 mol dm- NaNO2 a) I only aw b) ll only c) both I and II d) neither I nor 11