Question

For the reaction 2A(g) â B(g), the equilibrium constant is Kp = 0.76. A reaction mixture initially contains 4.0 atm of gas (PA = 2.0 atm and PB = 2.0 atm).
Which statement is true of the reaction mixture?

(a) The reaction mixture will proceed toward products.

(b) The reaction mixture is at equilibrium.

(c) The reaction mixture will proceed toward reactants

(d) It is not possible to determine from the information given the future direction of the reaction mixture

Answer 1

Answer: (a) The reaction mixture will proceed toward products.

Explanation:

Equilibrium constant is defined as the ratio of pressure of products to the pressure of reactants each raised to the power their stoichiometric ratios. It is expressed as $K_p$

K is the constant of a certain reaction when it is in equilibrium, while Q is the quotient of activities of products and reactants at any stage other than equilibrium of a reaction.

For the given chemical reaction:

$2A(g)\rightleftharpoons B(g)$

The expression for $Q_p$ is written as:

$Q_p=\frac{p_B}{(p_A)^2}$

$Q_p=\frac{(2.0)}{(2.0)^2}$

$Q_p=0.5$

$K_p=0.76$

Thus as $K_p>Q_p$ , the reaction will shift towards the right i.e. towards the product side.