Question

5.0 moles of nitrogen gas is reacted with 2.5 moles of oxygen gas in an 10. L container. At equilibrium, 1.5 moles of nitrogen dioxide is collected. What is the equilibrium constant for the formation of NO2 gas? A. 0.568 b. 0.756 c. 5.29 d. 1.76

Answer 1

(N2) = mols/L = 5.0 mols/10. L = 0.5 M initial
(O2) = 2.5 mols/10. L = 0.25 M initial
(NO2) = 1.5 mols/10. L = 0.15 M at equilibrium
.............................N2 + 2O2 ==> 2NO2
Initial...................0.5......0.25.........0
change.................-x.........-2x........2x
equilibrium .......0.5-x.....0.25-2x....2x
The problem tells you that 2x = 0.15 M
Knowing x you can calculate 0.5-x and 0.25-2x so now you know the equilibrium concentrations of all three components. Plug those values into Kc expression and solve for Kc. Post your work if you get stuck.