1036 HW 5 _sol_

# 1036 HW 5 _sol_ - Homework 5 solutions . Consider the...

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. Consider the system H 2 (g) + I 2 (g) 2HI(g) 1. Equilibrium pressures are 0.28 atm, 0.10 atm, and 1.20 atm for H 2 , I 2 , and HI respectively at 445 o C. Calculate K for this reaction at 445 o C. You are given the pressures (amounts) of the reactants and product at equilbrium . Since these are equilibrium values you can use them in the equilibrium expression: K = (pHI) 2 (pH 2 )( pI 2 ) pHI = 1.20 atm; pH 2 = 0.28 atm; pI 2 = 0.10 atm K = (1.20) 2 (0.28)(0.10) = 51 2. Another flask contains 0.25 atm of H 2 , 0.75 atm of I 2 and 0.90 atm of HI. Is the reaction at equilibrium and if not, which way will the system move to reach equilibrium? This time you have pressure values, but you don’t know if these are equilibrium pressures or not. To decide, calculate Q, the reaction quotient and compare the value to the value of K which is 51 as calculated in Question 1 above. Q = (pHI) 2 (pH 2 )( pI 2 ) Use the values given: pHI = 0.90 atm; pH 2 = 0.25 atm; p I 2 = 0.75 atm Q = (0.90) 2 (0.25)(0.75) = 4.3 In this case, Q < K (4.3 < 51). The system is NOT at equilibrium . The reaction will proceed to the right , producing more HI and using H 2 and I 2 . Thus the ratio of products to reactants will increase until Q = K = 51 Note about Q, reaction quotient : If Q = K: the system is at equilibrium. If Q

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## This homework help was uploaded on 04/10/2008 for the course CHEM 1036 taught by Professor Amateis during the Spring '08 term at Virginia Tech.

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1036 HW 5 _sol_ - Homework 5 solutions . Consider the...

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