Question

If the reaction N2 (g) + 3 H2 (g) --> 2 NH3 (g) has the concentrations 0.55 M for nitrogen, 0.75 M for hydrogen and 0.25 M for ammonia gas, what is the Kc? Show all work. Does this mean that there are more reactants or products at equilibrium? Explain how you determined that.

Answer 1

K_c is the equilibrium constant; K_c= [products]/[reactants]

For the above reaction, K_c = [NH₃]² / [N₂] [H₂]³  

[NH₃] = 0.25 M

[N₂] = 0.55 M

[H₂] = 0.75 M

Hence  K_c = [0.25 ]² / [0.55 ] [0.75]³ = 0.0625 / 0.55 x 0.42 = 0.269

If K_c is larger than 1(K_c > 1) the mixture contains more of the products.

If K_c is less than 1(K_c < 1), the mixture contains more of the reactants.

If K_c is equal to 1(K_c = 1), the amounts of products and reactants are almost the same.

Here K_c < 1, hence there is more reactants than the products in the mixture.