Question

Consider the following reaction which is at equilibrium at 25 degree C: NH_4(NH_2CO_2)(s) 2 NH_3(g) + CO_2(g), delta H degree = 152.2 kJ In which direction will the reaction shift if? *(a) the pressure is increased (b) the pressure decreased (c) the temperature is increased (d) the temperature is decreased (e) some CO_2 is added (f) NH_3 is removed (g) a catalyst is added (h) some NH_4(NH_2CO_2) is added (i) some Ne is added; and, (j) the volume is increased

Answer 1

NH₄(NH₂CO₂) (s) $\rightleftharpoons$   2 NH₃(g) + CO₂(g),    $\Delta$ H^o = 152.2 kJ

(a)

According to Le Chatelier, the position of equilibrium will move in such a way as to counteract the change. That means that the position of equilibrium will move so that the pressure is reduced again.

Increasing the pressure on a gas reaction shifts the position of equilibrium towards the side with fewer molecules.

Equilibrium towards the left-hand side.

(b)

The equilibrium will move in such a way that the pressure increases again. It can do that by producing more molecules. In this case, the position of equilibrium will move towards the right-hand side of the reaction.

(c)

According to Le Chatelier, the position of equilibrium will move in such a way as to counteract the change. That means that the position of equilibrium will move so that the temperature is reduced again.

Increasing the temperature of a system in equilibrium favours the endothermic reaction.

Forward reaction is endothermic

Equilibrium towards the right-hand side.

(d)

Decreasing the temperature of a system in equilibrium favours the exothermic reaction.

Backward reaction is exothermic

Equilibrium towards the left-hand side.

(e)

CO₂(g) is the product.

According to Le Chatelier, the position of equilibrium will move in such a way as to counteract the change in concentration of CO2.

Equilibrium towards the left-hand side.

(f)

According to Le Chatelier, the position of equilibrium will move so that the concentration of NH₃ increases again.

Equilibrium towards the right-hand side.

(g)

Adding a catalyst makes absolutely no difference to the position of equilibrium. Since, a catalyst speeds up the forward and back reaction to the same extent.

(h)

NH₄(NH₂CO₂) is reactant.

So, Equilibrium towards the right-hand side (or product side).