Question

9.Consider the exothermic equilibrium

2I(g) ? I₂(g)

What would be the effect on the position of equilibrium of

a.increasing the total pressure on the system by decreasing its volume. (2 points)

b.adding gaseous I₂ to the reaction mixture. (2 points)

c.decreasing the temperature. (2 points)

Please explain answers to get points, thanks!

Answer 1

Le Chatelier's Principle states that when a system at equilibrium is subjected to a "stress", the system will shift in such a way as to relieve the effects of the stress. In English, it simply means that if you remove one of the reactants or products, the system will try to replace it by shifting in watever direction it takes to produce more of that substance. By the same token, if more of one of the reactants or the products is added, the system will try to use up the excess by shifting in whatever direction it takes to do so. Increasing the pressure tends to shift the equilibrium in the direction of smaller number of molecules which will decrease the excess pressure. The opposite will take place when the pressure is reduced.

a. The sum of molecules on the left side of the equation is 2, while the sum of the molecules on the right side of the equation is 1. When pressure is increased, the system will shift to the right, in the direction of smaller number of molecules which would exert less pressure.

b. Increasing the concentration of I2 by addition would tend to make the system produce less of it. The equilibrium would shift to the left to replace the increased Iodine.

c. The equilibrium will move in such a way that the temperature increases again. Hence shift takes place to the right.