Question

N2 (g) + 3 H2 (g) ↔ 2NH3 (g) ΔH = -92 kJ/mol

a. Is this reaction exothermic or endothermic?
b. What direction will the equilibrium shift if nitrogen gas is removed?
c. What direction will the equilibrium shift if the temperature is lowered?
d. What direction will the equilibrium shift if ammonia (NH3) is added?
e. What principle helped you answer B-D?

Answer 1

a]

Delta(H) is assumed to be on the left and side. It is just a convention.

What it means is that since it is minus, the heat must be given away.

When that is true, the reaction is exothermic.

b]

If Nitrogen is removed, the equation will try to fill the void left by the removal of some Nitrogen. Therefore the NH3 will decompose and the reaction will shift to the left.

c]

The equation will really like to see a lower temperature. It means that the heat that is trying to be given up, will find it easier to heat the surroundings. The equation will shift right. Remember that delta H is a reactant.

d]

The equation will try and shift backwards to the left if more ammonia is added. That's how the equation will try and respond to more product.

e]

Le Chatelier's principle