Consider the following system at equilibrium where \delta h° = 18.8 kj, and kc = 9.52×10-2, at 350 k.

ch4(g) + ccl4(g) \rightleftharpoons 2ch2cl2(g)

when 0.31 moles of ccl4(g) are removed from the equilibrium system at constant temperature:

1. the value of

a. increases.
b. decreases.
c. remains the same.

2. the value of qc

a. is greater than
b. is equal to kc.
c. is less than kc.

3. the reaction :

a. run in the forward direction to reestablish equilibrium.
b. run in the reverse direction to reestablish equilibrium.
c. remain the same. it is already at equilibrium.

4. the concentration of ch4 will:

a. increase.
b. decrease.
c. remain the same.

1. C. remains the same.  2. C. is less than Kc.  3. B. run in the reverse direction to reestablish equilibrium. 4. A. increase.

Explanation:

At constant temperature, the equilibrium concentration has not effect on the equilibrium constant because the rate constants do not change with change in the concentrations or amounts of the reactants or products. Change in the concentration of one reactant or product causes the concentration of the others to change so as to maintain a constant value for the equilibrium constant. On the other hand, the reaction quotient is used to measure the relative amounts of reactants and products during a chemical reaction at any point in time. The value of the reaction quotient shows the direction of the chemical reaction.

Therefore, when 0.31 moles of CCl4(g) are removed from the equilibrium system at constant temperature:

1. the value of Kc remains the same

2. the value of Qc  is less than Kc

3.  the reaction must run in the reverse direction to reestablish equilibrium

4.  the concentration of will increase because product will be converted to reactants to reestablish equilibrium.

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