Advanced Placement Chemistry 1991 Free Response Questions 1) The acid ionization constant, Ka, for propanoic acid, C2H5COOH, is 1.3 x (a) Calculate the hydrogen ion concentration, [H+], in a 0.20-molar solution of propanoic acid. (b) Calculate the percentage of propanoic acid molecules that are ionized in the solution in (a). (c) What is the ratio of the concentration of propanoate ion, to that of propanoic acid in a buffer solution with a pH of 5.20 ? (d) In a 100-milliliter sample of a different buffer solution, the propanoic acid concentration is 0.50-molar and the sodium propanoate concentration is 0.50-molar. To this buffer solution, 0.0040 mole of solid NaOH is added. Calculate the pH of the resulting solution. 2) The molecular formula of a hydrocarbon is to be determined by analyzing its combustion products and investigating its colligative properties. (a) The hydrocarbon burns completely, producing 7.2 grams of water and 7.2 liters of CO2 at standard conditions. (b) Calculate the mass in grams of O2 required for the complete combustion of the sample of the hydrocarbon described in (a). (c) The hydrocarbon dissolves readily in CHCl3. The freezing point of a solution prepared by mixing 100. grams of CHCl3 and 0.600 gram of the hydrocarbon is -64.0 °C. The molal freezing-point depression constant of CHCl3 is 4.68 °C / molal and its normal freezing point is - °C. Calculate the molecular weight of the hydrocarbon. (d) What is the molecular formula of the hydrocarbon? 3) 2 ClO2(g) + F2(g) ---> 2 ClO2F(g)
Advanced Placement Chemistry 1991 Free Response Questions 1) The acid ionization constant, Ka, for propanoic acid, C2H5COOH, is 1.3 x (a) Calculate the hydrogen ion concentration, [H+], in a 0.20-molar solution of propanoic acid. (b) Calculate the percentage of propanoic acid molecules that are ionized in the solution in (a). (c) What is the ratio of the concentration of propanoate ion, to that of propanoic acid in a buffer solution with a pH of 5.20 ? (d) In a 100-milliliter sample of a different buffer solution, the propanoic acid concentration is 0.50-molar and the sodium propanoate concentration is 0.50-molar. To this buffer solution, 0.0040 mole of solid NaOH is added. Calculate the pH of the resulting solution. 2) The molecular formula of a hydrocarbon is to be determined by analyzing its combustion products and investigating its colligative properties. (a) The hydrocarbon burns completely, producing 7.2 grams of water and 7.2 liters of CO2 at standard conditions. (b) Calculate the mass in grams of O2 required for the complete combustion of the sample of the hydrocarbon described in (a). (c) The hydrocarbon dissolves readily in CHCl3. The freezing point of a solution prepared by mixing 100. grams of CHCl3 and 0.600 gram of the hydrocarbon is -64.0 °C. The molal freezing-point depression constant of CHCl3 is 4.68 °C / molal and its normal freezing point is °C. Calculate the molecular weight of the hydrocarbon. (d) What is the molecular formula of the hydrocarbon? 3) 2 ClO2(g) + F2(g) ---> 2 ClO2F(g) -
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