Multiple Choice
What is the equilibrium constant expression for a reaction at equilibrium?
16. Chemical Equilibrium
Equilibrium Constant Calculations
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Consider the following reaction: 2CH4(g) ⇌ C2H2(g) + 3H2(g). The reaction of CH4 is carried out at some temperature with an initial concentration of [CH4] = 0.089 M. At equilibrium, the concentration of H2 is 0.010 M. Find the equilibrium constant (Kc) for the reaction.
A
0.01
B
0.1
C
0.001
D
0.0001
Verified step by step guidance1
Identify the balanced chemical equation: 2CH4(g) ⇌ C2H2(g) + 3H2(g).
Set up an ICE (Initial, Change, Equilibrium) table to track the concentrations of each species. Initially, [CH4] = 0.089 M, [C2H2] = 0 M, and [H2] = 0 M.
Determine the change in concentration for each species. Let x be the change in concentration of C2H2 at equilibrium. Therefore, the change for CH4 is -2x, for C2H2 is +x, and for H2 is +3x.
Use the equilibrium concentration of H2 to find x. Since [H2] at equilibrium is 0.010 M, set 3x = 0.010 M and solve for x.
Calculate the equilibrium concentrations of all species: [CH4] = 0.089 - 2x, [C2H2] = x, and [H2] = 0.010 M. Then, use these concentrations to find the equilibrium constant Kc using the expression Kc = ([C2H2][H2]^3) / ([CH4]^2).
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