Equilibrium Equation

Question

Assume that the reaction for the formation of gaseous hydrogen fluoride from hydrogen and fluorine has an equilibrium constant of 1.15E2 at a certain temperature. In a particular experiment, 2.500 moles of each component were added to a 1.500 L flask. 

a. and b.) What is the balanced chemical equation and the equilibrium expression?

c.) Determine the value of Q.

d.) Does the reaction proceed to the left or the right? Justify your answer.

Answer 1

H₂ (g) + F₂ (g) <==> 2 HF (g)

K_c = [HF]² / ([H₂] [F₂]) = 1.15E2 (or 115)

Molarity of each component = 2.500 mol / 1.500 L = 1.667 M. Substitute this concentration and solve for Q.

Q = [HF]² / ([H₂] [F₂]) = (1.667)² / (1.667 x 1.667) = 1

Since Q = 1 < K_c = 115, this means that there are less products present. In order to reach equilibrium, Q must equal K_c, which means that the reaction must proceed towards the right (products).