AP Chemistry question! Help would be highly appreciated!!?

Question

For the reaction

H2(g) + CO2(g) H2O(g) + CO(g)

at 700°C, Kc = 0.520. Calculate the number of moles of H2 that are present at equilibrium if a mixture of 0.270 mole of CO and 0.270 mole of H2O is heated to 700°C in a 10 L container.

Thanks!!

Answer 1

Kc = [H2O][[CO]/[H2][CO2] = 0.520

Let [H2] = x. Then [CO2] = x, [H2O] = [CO] = 0.270 - x)

(0.270 - x)^2/x^2 = 0.520

(0.0279 - 0.540x + x^2)/x^2 = 0.520

0.0279 - 0.540x + x^2 = 0.520x^2

0.0279 - 0.540x + 0.480x^2 = 0