Question

In which direction will the position of the equilibrium $$ 2 \mathrm{HI}(g) \rightleftharpoons \mathrm{H}_{2}(g)+\mathrm{I}_{2}(g) $$ be shifted for each of the following changes? a. \(\mathrm{H}_{2}(g)\) is added. b. \(\mathrm{I}_{2}(g)\) is removed. c. \(\mathrm{HI}(g)\) is removed. d. In a rigid reaction container, some \(\operatorname{Ar}(g)\) is added. e. The volume of the container is doubled. f. The temperature is decreased (the reaction is exothermic).

Short answer

a. The equilibrium will shift to the right. b. The equilibrium will shift to the right. c. The equilibrium will shift to the left. d. The equilibrium will not shift. e. The equilibrium will shift to the right. f. The equilibrium will shift to the right.

Step-by-step solution

Determine the effect of the change

Increasing the concentration of a reactant (H2) will cause the system to move towards the product side (to the right). Therefore, the equilibrium will shift to the right to minimize the effect of the added H2. #b. Removing I2(g)#

Determine the effect of the change

Decreasing the concentration of one of the products (I2) will cause the system to replenish the depleted product, thus shifting the equilibrium to the product side (to the right). #c. Removing HI(g)#

Determine the effect of the change

Decreasing the concentration of a reactant (HI) will cause the system to shift towards the reactants side (to the left) in order to minimize the effect and increase the concentration of HI. #d. Adding Ar(g) in a rigid container#

Determine the effect of the change

Adding an inert gas (Ar) that doesn't participate in the reaction, in a rigid container (at constant volume) will not cause a change in the partial pressures of the reactants or products. Therefore, the equilibrium will not shift. #e. Doubling the volume of the container#

Determine the effect of the change

Doubling the volume of the container results in a decrease in the partial pressure of all gases in the system. To minimize this effect, the equilibrium will shift in the direction that increases the number of moles of gas. In this case, the equilibrium will shift to the right (as there are 2 moles of HI for every mole of H2 and I2). #f. Decreasing the temperature (reaction is exothermic)#

Determine the effect of the change

If the reaction is exothermic, it releases heat as it proceeds towards the products. When the temperature is decreased, the system will try to minimize the effect by producing more heat. Consequently, the equilibrium will shift to the right, favoring the formation of products.