Exercise 14.59: Problems by Topic - Finding Equilibrium Concentrations from Init

Question

Exercise 14.59: Problems by Topic - Finding Equilibrium Concentrations from Initial Concentrations and the Equilibrium Constant Consider the following reaction: A(g) B(g) + C(g) Find the equilibrium concentrations of A. B. and C tor each of the following different values of Kc Assume that the initial concentration of A in each case is 1.0 M and that the reaction mixture initially contains no products. Make any appropriate simplifying assumptions. Kc= 12 Express your answer using two significant figures. Enter your answers numerically separated by commas. Kc = 1.2 times 10-2 Express your answer using two significant figures. Enter your answers numerically separated by commas. Kc = 2.0 times 10-5 Express your answer using two significant figures. Enter your answers numerically separated by commas.

Explanation / Answer

The general formula is Kc = [B]*[C]/[A] The change or equilibrium concentration for each is A = 1 - x B = +x C = +x Therefore the formula is Kc = x*x/(1-x) Rearrange to get x^2 = (1-x)*Kc x^2 + Kc*x - Kc*1 = 0 For every value of Kc just plug in Kc and solve for x. For Kc = 1.2 x = 0.648 [A] = 1 -x = 1 - .648 = 0.352 [B] = [C] = x = 0.648 Now repeat with the other Kc values For Kc = 1.2 x 10^-2, x = 0.1037 A = 1 - x = .8963 B = C = x = .1037 For Kc = 2 x 10^-5, x = .0044 A = .9956 B = C = .0044 All the concentrations are in molar (M) Hope this helped

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