Spring 09 Recitation Quiz 2

Spring 09 Recitation Quiz 2 - CHEM 0120 Golde SPRING 2009...

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CHEM 0120 SPRING 2009 Tuesday 8:00 AM Golde QUIZ 2 WEEK 3 January 20, 2009 Name_______________________________ 1. Consider the following reaction: A(g) + 3 B(g) 2 C(g) + D(g), K c = 7.3 x 10 -9 A container contains an initial mix of A and B, with concentrations, [A] = 0.20M and [B] = 0.30M. Which one or more of the species, A, B, C and D, will have a very small concentration when equilibrium is attained? Give your reasoning - no calculations are expected. 2. 8.35 g of nitrogen dioxide (NO 2 ) was placed in a 2.50 L container. a) What is the molar concentration of NO 2 (moles/L) in the container. b) The reaction: 2NO 2 (g) N 2 O 4 (g) came to equilibrium, at which point the NO 2 concentration was 0.0472 M. Calculate [N 2 O 4 ] at equilibrium and the equilibrium constant, K c . ANSWERS 1. As K c is very small, we expect that the species, C and D, on the right side of the equation will have a very small concentration at equilibrium. Very little reaction will occur. 2. a) Molar concentration = 8.35g x 1 mol 1 x 46.0 g 2.50L = 0.0726 M b) 2NO 2 N 2 O 4 I 0.0726 0 ___Given info C -0.0254 +0.0127 E 0.0472 0.0127 K c = 0.0127 = 5.70 (0.0472) 2 For Make-up Only Regular recitation Day: Time: instructor: Quiz Score: Group score: Scores recorded by:
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CHEM 0120 SPRING 2009 Tuesday 1:00 PM Golde QUIZ 2 WEEK 3 January 20, 2009 Name_______________________________ 1. Consider the reaction: H 2 SO 4 (aq) + 2 NaOH(aq) Na 2 SO 4 (aq) + 2 H 2 O(l), K c1 (1) The net ionic equation for this reaction is: 2 H 3 O + (aq) + 2 OH - (aq) 2 H 2 O(l) + 2 H 2 O(l), K c2 (2) Now we know the following reaction and K c value: H 3 O + (aq) + OH - (aq) H 2 O(l) + H 2 O(l), K c3 = 1 x 10 14 (3) So, the question is: what is the value of K c1 , the equilibrium constant of the reaction (1)? (a) Let’s start with K
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This note was uploaded on 04/06/2009 for the course CHEM 0120 taught by Professor Golde during the Spring '07 term at Pittsburgh.

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Spring 09 Recitation Quiz 2 - CHEM 0120 Golde SPRING 2009...

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