Methane, ethyne, and hydrogen form the following equilibrium mixture:
2 CH4(g) ⇌ C2H2(g) + 3 H2(g)
While studying this reaction mixture, a chemist analyzed a 4.0 L sealed flask.
The chemist found 0.46 mol of CH4(g), 0.64 mol of C2H2(g), and 0.92 mol of H2(g).
What is the value of Kc for the reaction? (6 marks)
(Show all steps, work, units and a concise final answer)
To find the value of Kc, we need to write the expression for the equilibrium constant using the molar concentrations of the reactants and products.
The balanced equation for the reaction is:
2 CH4(g) ⇌ C2H2(g) + 3 H2(g)
The equilibrium constant expression for this reaction is:
Kc = [C2H2] * [H2]^3 / [CH4]^2
Given:
[C2H2(g)] = 0.64 mol and it is a 4.0 L flask, so the concentration of C2H2(g) is:
[C2H2(g)] = 0.64 mol / 4.0 L = 0.16 M
[H2(g)] = 0.92 mol and it is a 4.0 L flask, so the concentration of H2(g) is:
[H2(g)] = 0.92 mol / 4.0 L = 0.23 M
[CH4(g)] = 0.46 mol and it is a 4.0 L flask, so the concentration of CH4(g) is:
[CH4(g)] = 0.46 mol / 4.0 L = 0.12 M
Plugging these values into the equilibrium constant expression, we get:
Kc = (0.16)(0.23)^3 / (0.12)^2
Kc = 0.001674 / 0.0144
Kc = 0.116
Therefore, the value of Kc for the reaction is 0.116.
where did you get 0.16?
Apologies for the error. The value of 0.16 was an incorrect calculation. Let's correct it:
Given:
[C2H2(g)] = 0.64 mol and it is a 4.0 L flask, so the concentration of C2H2(g) is:
[C2H2(g)] = 0.64 mol / 4.0 L = 0.16 M
[H2(g)] = 0.92 mol and it is a 4.0 L flask, so the concentration of H2(g) is:
[H2(g)] = 0.92 mol / 4.0 L = 0.23 M
[CH4(g)] = 0.46 mol and it is a 4.0 L flask, so the concentration of CH4(g) is:
[CH4(g)] = 0.46 mol / 4.0 L = 0.115 M
Plugging these values into the equilibrium constant expression, we get:
Kc = (0.16)(0.23)^3 / (0.115)^2
Kc = 0.00077168 / 0.013225
Kc ≈ 0.0584
Therefore, the value of Kc for the reaction is approximately 0.0584.
i thought the answer is 2.36
I apologize for the previous error. Let's re-calculate the value of Kc correctly:
Given:
[C2H2(g)] = 0.64 mol and it is a 4.0 L flask, so the concentration of C2H2(g) is:
[C2H2(g)] = 0.64 mol / 4.0 L = 0.16 M
[H2(g)] = 0.92 mol and it is a 4.0 L flask, so the concentration of H2(g) is:
[H2(g)] = 0.92 mol / 4.0 L = 0.23 M
[CH4(g)] = 0.46 mol and it is a 4.0 L flask, so the concentration of CH4(g) is:
[CH4(g)] = 0.46 mol / 4.0 L = 0.115 M
Plugging these values into the equilibrium constant expression, we get:
Kc = (0.16)(0.23)^3 / (0.115)^2
Kc = 0.00191616 / 0.013225
Kc ≈ 0.1448
Therefore, the value of Kc for the reaction is approximately 0.1448.