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Unformatted text preview: CHEM 230 F09 Exam 3 Worksheet 2 1 1) Citric acid (H 3 C 6 H 5 O 7 ) is a triprotic acid with pK a1 = 3, pK a2 = 4, and pK a3 = 6.5. What is the approximate pH of a 0.01 mol/L solution of H 3 C 6 H 5 O 7 ? A) 2.5 B) 3 C) 4 D) 4.5 2) In a titration of a weak acid (pK a = 4) with a strong base, what would the pH of the stoichiometric point be? A) less than 7 B) exactly 7 C) greater than 7 3) Mg(OH) 2 has K sp = 1x10-12 . If 0.1 mol Mg(OH) 2 was added to 1 L of water, what would the pH of the water be, assuming the water was initially pH 7? A) 8.7 B) 9.8 C) 10.1 D) 13.0 E) 13.3 4) The current of an electrochemical cell is determined by what? A) The power of an attached device B) The standard cell potential C) The reaction quotient D) All of the above E) None of the above I= Power/ ! E, and ! E = ! E - (RT/nF)lnQ 5) Is HClO 4 most likely to be an oxidizing agent or a reducing agent? (Hint, take a look at the oxidation number of Cl) A) Oxidizing agent B) Reducing agent C) Both D) Neither 6) Calculate the equilibrium constant for the following reaction at 25.0 o C: Hg 2 2+ + 2 Fe 3+ ! 2 Hg 2+ + 2 Fe 2+ A) 11.7 B) 8.42x10-6 C) 1.19 x10 5 D) -0.15 CHEM 230 F09 Exam 3 Worksheet 2 2 7) During a first order reaction, a reactant decreases from 1 M to 0.5 M in time T 1 . The same reaction then decreases from 0.5 M to 0.25 M in time T 2 . Is T 1 longer, shorter, or the same as T 2 ? A) T 1 is longer than T 2 B) T 1 and T 2 are the same C) T 1 is shorter than T 2 D) Insufficient information to say. 8) Which of the following rate laws for elementary reactions would most likely be the fastest considering the molecularity? A) k[A][B] B) k[A] 2 [B] C) k[A] 2 [B] 2 D) k[A] 3 E) All of the above would be the same....
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