CH302 Holcombe Hwk #3

# CH302 Holcombe Hwk #3 - perlick(app582 Homework#3...

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perlick (app582) – Homework #3 – holcombe – (51160) 1 This print-out should have 23 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points Consider the reaction CaCO 3 (s) CaO(s) + CO 2 (g) , at equilibrium at a certain temperature. Now a small amount oF Ca 14 CO 3 (s) ( 14 C la- beled calcium carbonate) is added. What species will be present aFter equilibrium is re-established? 1. CaO(s), 14 CO 2 (g), CO 2 (g) 2. CaCO 3 (s), CaO(s), 14 CO 2 (g), CO 2 (g) 3. CaCO 3 (s), Ca 14 CO 3 (s), CaO(s), 14 CO 2 (g), CO 2 (g) correct 4. CaCO 3 (s), Ca 14 CO 3 (s), CaO(s), CO 2 (g) 5. Ca 14 CO 3 (s), CaO(s), 14 CO 2 (g), CO 2 (g) Explanation: The addition oF extra reactant Ca 14 CO 3 will Favor the production oF more products (CaO(s) and 14 CO 2 (g)). However, since this is a dynamic equilibrium, both Forward and backward reactions occur. ThereFore, an equilibrium will be established where 14 C is present in both products and reactants con- taining C. 002 10.0 points In which oF the Following cases will the LEAST time be required to arrive at equilibrium? K below reFers to the equilibrium constant. 1. K is a very large number. 2. K is a very small number. 3. K is about 1. 4. Cannot tell since the time to arrive at equilibrium does not depend on K . correct 5. Cannot tell without knowing the value oF K . Explanation: The equilibrium constant K re±ects the relative amounts oF products and reactants present when the reaction is complete, and gives no inFormation on the time needed. The rate constant k indicates how Fast the reaction occurs. 003 10.0 points Using the law oF mass action, write the equi- librium expression For the Following reaction: 2 Cu 2+ (aq) + 4 I (aq) ←→ 2 CuI(s) + I 2 (aq) 1. K = [Cu 2+ ] 2 [I ] 4 [I 2 ] 2. K = [Cu 2+ ] 2 [I ] 4 [I 2 ][CuI] 2 3. K = [I 2 ] [Cu 2+ ] 2 [I ] 4 correct 4. K = [I 2 ][CuI] 2 [Cu 2+ ] 2 [I ] 4 Explanation: The equilibrium expression, K , is the ratio oF products to reactants raised to their respec- tive stoichiometric coe²cients. Solid species are not included in the expression. 004 10.0 points Write the reaction quotient For 4 Bi(s) + 3 O 2 (g) 2 Bi 2 O 3 (s) 1. Q = P 2 Bi 2 O 3 P 4 Bi P 3 O 2 2. Q = 2 P Bi 2 O 3 4 P Bi 3 P O 2 3. Q = P Bi 2 O 3 2 P 4 Bi 4. Q = P 3 O 2

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perlick (app582) – Homework #3 – holcombe – (51160) 2 5. Q = 1 P 3 O 2 correct Explanation: Q = activities of products activities of reactants , where “activities” are for an ideal gas: a J = [ P J ] for a solute: a J = [J] for a pure solid or liquid: a J = 1 005 10.0 points Consider the following reactions at 25 C: reaction K c 2 NO(g) N 2 (g) + O 2 (g) 1 × 10 30 2 H 2 O(g) 2 H 2 (g) + O 2 (g) 5 × 10 82 2 CO(g) + O 2 (g) 2 CO 2 (g) 3 × 10 91 Which compound is most likely to dissociate and give O 2 (g) at 25 C? 1.
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## This note was uploaded on 02/12/2012 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas.

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CH302 Holcombe Hwk #3 - perlick(app582 Homework#3...

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