Chemistry 30

For the following system at equilibrium:

H_{2 (g)} + I_{2 (g)} ↔ 2 HI _(g)

a. Predict the shift in equilibrium when more HI_(g) is added to the system.

b. How will the concentration of I₂ change?

Solution:

Adding something on the product side of the reaction will cause equilibrium to shift to the reactant side. In other words, the reverse reaction will be favored, or you could say that equilibrium shifts to the left.

The concentration of I₂ will increase.

For the reaction below, predict the direction the equilibrium will shift given the following changes. Temperature and volume are held constant.

2 NO_{2 (g)} + 7 H_{2 (g)} ↔ 2 NH_{3 (g)} + 4 H₂O_(g)

a. addition of ammonia

b. removal of nitrogen dioxide

c. removal of water vapour

d. addition of hydrogen

Solution

At a particular temperature, the following reaction has an equilibrium constant, K_eq of 0.18

PCl_{3 (g)} + Cl_{2 (g)} ↔ PCl_{5 (g)}

More PCl₃ is added to the system. Will the value of K_eq increase or decrease?

Solution:

Changing the concentration of a reaction participant will not change the value of K_eq. K_eq will still equal 0.18 after equilibrium becomes re-established.