Question

A student ran the following reaction in the laboratory at 275 K:

2CH₂Cl₂(g) ⇌ CH4(g) + CCl₄(g)

When she introduced 7.94x10⁻² moles of CH₂Cl₂(g) into a 1.00 liter container, she found the equilibrium concentration of CH₂Cl₂(g) to be 4.77x10⁻³ M Calculate the equilibrium constant, Kc, she obtained for this reaction

Answer 1

To determine the equilibrium constant Kc, calculate the change in concentration of CH2Cl2 and use it to find the equilibrium concentrations of the products. Apply the equilibrium expression to find the Kc value.

Step-by-step explanation:

To calculate the equilibrium constant (Kc) for the reaction 2CH2Cl2(g) ⇌ CH4(g) + CCl4(g), we need to use the equilibrium concentrations of the reactants and products. The student started with 7.94x10⁻² moles of CH2Cl2 in a 1.00 liter container. At equilibrium, the concentration of CH2Cl2 was found to be 4.77x10⁻³ M. The change in concentration (Δ) of CH2Cl2 is the initial concentration minus the equilibrium concentration.

The initial concentration (Ci) is calculated by dividing the number of moles of CH2Cl2 by the volume of the container: Ci = 7.94x10⁻² mol / 1.00 L = 7.94x10⁻² M. The change in concentration (Δ) is therefore 7.94x10⁻² M - 4.77x10⁻³ M = 7.4623x10⁻² M.

Since for every 2 moles of CH2Cl2 that react, one mole of CH4 and one mole of CCl4 are produced, the equilibrium concentrations of CH4 and CCl4 will both be Δ/2 = 7.4623x10⁻² M / 2 = 3.73115x10⁻² M.

Finally, we can apply the equilibrium expression:
Kc = [CH4][CCl4]/[CH2Cl2]2 = (3.73115x10⁻² M)² / (4.77x10⁻³ M)2 to find the Kc value.