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Unformatted text preview: Version 484 Exam 3 Laude (52455) 1 This print-out should have 35 questions. Multiple-choice questions may continue on the next column or page find all choices before answering.- d [A] adt = k [A] = [A]- akt t 1 / 2 = [A] 2 ak- d [A] adt = k [A] ln[A] = ln[A]- akt t 1 / 2 = ln2 ak- d [A] adt = k [A] 2 1 [A] = 1 [A] + akt t 1 / 2 = 1 ak [A] ln a b = ln a- ln b rate = k [A] x [B] y =- 1 a d [ A ] dt k = A exp parenleftbigg- E a RT parenrightbigg ln k 2 k 1 = E a R parenleftbigg 1 T 1- 1 T 2 parenrightbigg E o cell = E o cathode- E o anode E cell = E o cell- parenleftbigg . 05916 n parenrightbigg log Q Q = [ C ] c [ D ] d [ A ] a [ B ] b G o =- n F E o cell =- R T ln K E o cell = parenleftbigg R T ln K n F parenrightbigg parenleftbigg I t n F parenrightbigg = moles of product F = 96 , 485 . 3 C per mole of e 1 Ampere = 1 C s 1 R = 8 . 314 J mol 1 K 1 N = 6 . 022 10 23 001 6.0 points If the table of standard reduction potentials is ordered with the strongest reducing agents at the top, how are the reduction potentials ordered (from top to bottom)? 1. from most common to least common 2. from most spontaneous to least sponta- neous 3. from most positive to most negative 4. from most negative to most positive cor- rect Explanation: Good reducing agents have positive (spon- taneous) oxidation potentials. The reduc- tion potentials is the opposite of the oxi- dation potential, so the oxidized form of a good reducing agent will have a negative (non- spontaneous) reduction potential. 002 6.0 points A steel surface has been electroplated with 1.02 g of vanadium (V, molar mass = 51 g/mol). If 9.65 10 3 C of charge were used, what was the original oxidation number of V? 1. +4 2. +2 3. +3 4. +6 5. +5 correct 6. +1 Version 484 Exam 3 Laude (52455) 2 Explanation: moles V = 1 . 02 g 51 g / mol = 0.02 moles moles e = 9 . 65 10 3 C 9 . 65 10 4 C / mol = 0.1 moles ox. number = . 1 moles e . 02 moles V = +5 003 6.0 points According to transition state theory and the potential energy curves used to explain it, which of the following is incorrect? 1. Reactants pass through a high-energy transition state before forming products. 2. Reactants pass through a short-lived in- termediate state before forming products. 3. The energy of activation for the forward reaction is always less than that for the reverse reaction. correct 4. Free energy of activation is always posi- tive. 5. The change in internal energy for a reac- tion, differs from E for the reverse reaction only by a change in sign. Explanation: 004 6.0 points The mechanism proposed for the oxidation of the iodide ion by the hypochlorite ion in aqueous solution is as follows: 1: ClO + H 2 O HClO + OH (fast) 2: I + HClO HIO + Cl (slow) 3: HIO + OH IO + H 2 O (fast) What is the rate law for the formation of HIO implied by this mechanism?...
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This note was uploaded on 05/11/2010 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas.
- Spring '07