How to Calculate Equilibrium Concentrations After Compressing a Mixture

What will be the concentrations of the three gases once equilibrium has been reestablished, if the equilibrium mixture is compressed at constant temperature to a volume of 9.91 L?

Given initial concentrations:

  • [COCl2] = 0.154 M
  • [CO] = 5.92E-2 M
  • [Cl2] = 5.92E-2 M

Answer:

To determine the concentrations of COCl2, CO, and Cl2 at equilibrium after compressing the mixture, use the principle of Le Chatelier. When the volume is reduced, the equilibrium will shift towards the products side to minimize the number of gas molecules. Calculate the new concentrations of the gases using the given initial concentrations and the new volume.

Calculating Equilibrium Concentrations After Compression

The given question involves the reaction equilibrium of COCl2(g) <=> CO(g) + Cl2(g). The equilibrium constant (K) for the reaction is given as 2.28E-2 at 617 K. The initial concentrations of COCl2, CO, and Cl2 in the equilibrium mixture are provided. To determine the concentrations of the three gases once equilibrium is reestablished after the compression of the mixture to a new volume, we can use the principle of Le Chatelier.

The principle states that if a system at equilibrium is subjected to a change, it will adjust to counteract the effect of that change and reestablish equilibrium. In this case, the volume of the mixture is reduced from 17.7 L to 9.91 L at constant temperature. As the volume decreases, the system will try to counteract the change by shifting the equilibrium to the side with fewer moles of gas molecules.

Since the reaction consists of one mole of reactant (COCl2) producing two moles of products (CO and Cl2), the equilibrium will shift towards the product side to reduce the number of gas molecules. As a result, the concentrations of CO and Cl2 would increase, while the concentration of COCl2 decreases.

First, calculate the new concentration of COCl2 by multiplying its initial concentration by the ratio of the final volume to the initial volume.

Next, calculate the new concentrations of CO and Cl2 by multiplying their initial concentrations by the square of the same ratio.

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