Question

What is the new equilibrium constant for the reaction N2(g) + 3H2(g) ⇌ 2NH3(g) if the initial concentration of NH3 is 0.1 M, N2 is 0.2 M, H2 is 0.3 M, and then more H2 is added until its concentration reaches 0.5 M?

Answer 1

The equilibrium constant  Kc  for a reaction does not change when the concentrations of the reactants or products are changed. It only changes with temperature. Therefore, the equilibrium constant for the reaction N2 g  + 3H2 g   2NH3 g  will remain the same even after the concentration of H2 is increased to 0.5 M.However, the reaction will shift to re-establish equilibrium after the change in concentration. To determine the new equilibrium concentrations, we can use an ICE  Initial, Change, Equilibrium  table:``          N2 g    +   3H2 g       2NH3 g Initial:  0.2 M        0.3 M          0.1 MChange:  -x           -3x             +2xFinal:   0.2-x         0.5-3x          0.1+2x``At equilibrium, the reaction will satisfy the equation:Kc = [NH3]^2 /  [N2] * [H2]^3 Since Kc remains constant, we can use the initial concentrations to find its value:Kc =  0.1 ^2 /  0.2 *  0.3 ^3 Now, we can use the final equilibrium concentrations to find the new equilibrium concentrations:Kc =   0.1+2x ^2  /   0.2-x  *  0.5-3x ^3 Since Kc is constant, we can set the two equations equal to each other: 0.1 ^2 /  0.2 *  0.3 ^3  =   0.1+2x ^2  /   0.2-x  *  0.5-3x ^3 Solving for x will give us the change in concentrations, and we can find the new equilibrium concentrations. However, the equilibrium constant Kc itself will remain the same.