HW 4 - – Homework #4 – holcombe – 1 This print-out...

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Unformatted text preview: – Homework #4 – holcombe – 1 This print-out should have 24 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Suppose the reaction H 2 (g) + I 2 (g) ⇀ ↽ 2 HI(g) has an equilibrium constant K c = 49 and the initial concentration of H 2 and I 2 is 0.60 M and HI is 0.0 M. Which of the following is the correct value for the final concentration of HI(g)? 1. 0.525 M 2. 0.250 M 3. 0.778 M 4. 1.050 M 5. 0.219 M 6. 0.467 M 7. 0.933 M correct Explanation: K c = 49 [H 2 ] ini = 0 . 60 M [I 2 ] ini = 0 . 60 M [HI] ini = 0 M H 2 (g) + I 2 (g) ⇀ ↽ 2 HI(g) Ini, M 0.6 0.6 Δ, M- x- x +2 x Equil, M 0 . 6- x . 6- x 2 x K c = [HI] 2 [H 2 ] [I 2 ] 49 = (2 x ) 2 (0 . 6- x ) 2 7 = 2 x . 6- x 7(0 . 6- x ) = 2 x 4 . 2- 7 x = 2 x 4 . 2 = 9 x x = 4 . 2 9 = 0 . 46667 M Looking back at our equilibrium values, we see that the final concentration of HI is equal to 2 x , so 2(0.46667 M) = 0.933 M. 002 10.0 points For the reaction 4 NH 3 (g) + 3 O 2 (g) → 2 N 2 (g) + 6 H 2 O(g) , K = 10 80 at a certain temperature. Initially, all reactants and products have concentra- tions equal to 12 M. What is the approximate concentration of ammonia at equilibrium? 1. 0 M correct 2. 3 M 3. 18 M 4. 6 M 5. 12 M Explanation: 003 10.0 points The equilibrium constant for the reaction HNO 2 (aq) + H 2 O( ℓ ) → NO − 2 (aq) + H 3 O + (aq) is 4 . 3 × 10 − 4 at 25 ◦ C. Will nitrous acid spontaneously dissociate when [HNO 2 (aq)] = [NO − 2 (aq)] = [H 3 O + (aq)] = 1.0 M? 1. No correct 2. Yes 3. Unable to determine Explanation: 004 10.0 points A reaction between gaseous sulfur dioxide and oxygen gas to produce gaseous sulfur trioxide takes place at 600 ◦ C. At that temperature, the concentration of SO 2 is found to be 1.91 – Homework #4 – holcombe – 2 mol/L, the concentration of O 2 is 1.38 mol/L, and the concentration of SO 3 is 3.87 mol/L. Using the balanced chemical equation, find the equilibrium constant for this system....
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This note was uploaded on 11/12/2010 for the course CH 302 taught by Professor Holcombe during the Fall '07 term at University of Texas.

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HW 4 - – Homework #4 – holcombe – 1 This print-out...

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