Question and Inquiry

Question

5. A chemist was studying the following reaction:   

  N2O4(g) ⇆  2 NO2(g)

The chemist adds 0.171 mol of N2O4(g) to a 2.0 L container at 200°C. The system comes to equilibrium based on a K value of 0.04545 for the system at this temperature. What is the concentration of NO2(g) at equilibrium? You MUST verify your answer using a Q-test.

Answer 1

0.171 mol / 2 L = 0.0855 M

N2O4(g) <==> 2NO2(g)

0.0855M............0...........Initial

-x....................+2x........Change

0.0855-x..........2x........Equilibrium

K = [NO2]² / [N2O4]

0.04545 = (2x)² / 0.0855-x

Use the quadratic to solve for x

Multiply x by 2 to get the equilibrium concentration of NO2