For the equilibrium 2 NOBr(g) D 2 NO(g) + Br2(g), Kc = 1.56 ´ 10-3 at 300 K. Suppose 0.400 M NOBr is placed in a reaction vessel at 300 K. At a given point, the concentration of Br2 is 0.0134 M. Which of the following statements is true? The value of K will decrease until it is equal to Q. Q < K so the reaction will continue to make more products. Q > K so the reaction will consume products to make more reactants. The value of K will increase until it is equal to Q. Q = K so the system is at equilibrium.

Explanation:

2 NOBr(g) ⇄ 2 NO(g) + Br2(g)

Kc = 1.56 ´ 10-3

Which of the following statements is true?

The reaction quotient (Q) measures the relative amounts of products and reactants present during a reaction at a particular point in time. The Q value can be compared to the Equilibrium Constant, K, to determine the direction of the reaction that is taking place.

- The value of K will decrease until it is equal to Q: This statement is wrong.

Equilibrium constants are not changed if you change the concentrations of things present in the equilibrium. The only thing that changes an equilibrium constant is a change of temperature.

- Q < K so the reaction will continue to make more products.

If Q<K, then the reaction favors the products. the system shifts to the RIGHT to make more products. This statement is true.

- Q > K so the reaction will consume products to make more reactants.

If Q>K, then the reaction favors the reactants. the system shifts to the LEFT to make more reactants. This statement is true.

- The value of K will increase until it is equal to Q: This statement is wrong.

Equilibrium constants are not changed if you change the concentrations of things present in the equilibrium. The only thing that changes an equilibrium constant is a change of temperature.

- Q = K so the system is at equilibrium: This statement is true.

If Q=K, then the reaction is already at equilibrium. There is no tendency to form more reactants or more products at this point. No side is favored and no shift occurs.