When 0.20 mol of hydrogen gas and 0.15 mol of iodine gas are heated at 450 °C until equilibrium is established, the equilibrium mixture is found to contain 0.26 mol of hydrogen iodide. The equation for the reaction is as follows H2((g) + I2(g) ⇋ 2HI(g)
What is the correct expression for the equilibrium constant, Kc?

Explanation:

Hello there!

In this case, for these equilibrium problems it is firstly necessary to know the balanced reaction at equilibrium:

H2((g) + I2(g) ⇋ 2HI(g)

Next, by means of the law of mass action, it turns out possible for us to write the required and correct expression for the equilibrium constant by considering the concentrations and the coefficients in the aforementioned reaction:

Best regards!

it would be a gas formation