AP Chemistry 1982 Free Response Questions

AP Chemistry 1982 Free Response Questions - 1982 Free...

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1982 Free Response Questions 1) A buffer solution contains 0.40 mole of formic acid, HCOOH, and 0.60 mole of sodium formate, HCOONa, in 1.00 liter of solution. The ionization constant, K a , of formic acid is 1.8 x 10¯ 4 (a) Calculate the pH of this solution. (b) If 100. milliliters of this buffer solution is diluted to a volume of 1.00 liter with pure water, the pH does not change. Discuss why the pH remains constant on dilution. (c) A 5.00-milliliter sample of 1.00-molar HCl is added to 100. milliliters of the original buffer solution. Calculate the [H 3 O + ] of the resulting solution. (d) A 800-milliliter sample of 2.00-molar formic acid is mixed with 200. milliliters of 4.80-molar NaOH. Calculate the [H 3 O + ] of the resulting solution. 2) When a dilute solution of H 2 SO 4 is electrolyzed, O 2 (g) is produced at the anode and H 2 (g) is produced at the cathode. (a) Write the balanced equations for the anode, cathode, and overall reaction that occur in this cell. (b) Compute the coulombs of charge passed through the cell in 100.0 minutes at 10.0 amperes. (c) What number of moles of O 2 is produces by the cell when it is operated for 100. minutes at 10.0 amperes?
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(d) The standard enthalpy of formation of H 2 O(g) is -242 kilojoules per mole. How much heat is liberated by the complete combustion, at 298 K and 1.00 atmosphere, of the hydrogen produced by the cell operated as in (c)? 3) Water is added to 4.267 grams of UF 6 . The only products are 3.730 grams of a solid containing only uranium, oxygen, and fluorine and 0.970 gram of a gas. The gas is 95.0 percent fluorine, and the remainder is hydrogen. (a) From these data, determine the empirical formula of the gas. (b) What fraction of the fluorine of the original compound is in the solid and what fraction in the gas after the reaction? (c) What is the formula of the solid product? (d) Write a balanced equation for the reaction between UF 6 and H 2 O. Assume that the empirical formula of the gas is the true formula. 4) Use appropriate ionic and molecular formulas to show the reactants and the products for the following, each of which occurs in aqueous solution except as indicated. Omit formulas for any ionic or molecular species that do not take part in the reaction. You need not balance. In all cases a reaction occurs. (a) Hydrogen gas is passed over hot iron(III) oxide. (b) Solution of potassium iodide and potassium iodate are mixed in acid solution. (c) Dilute sulfuric acid is added to solid calcium fluoride.
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(d) Solid ammonium carbonate is heated. (e) Methane gas is mixed with an excess of chlorine gas. (f) A concentrated solution of ammonia is added to a suspension of zinc hydroxide. (g) Hydrogen peroxide is added to an acidified solution of sodium bromide. (h) Dilute hydrochloric acid is added to a dilute solution of
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This note was uploaded on 09/03/2011 for the course CHM 2046 taught by Professor Haces during the Spring '11 term at FAU.

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AP Chemistry 1982 Free Response Questions - 1982 Free...

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