The Position of Equilibrium Flashcards

All 8 cards in this deck

What are the steps to predict the effect of a temperature change on the position of equilibrium?

e.g. cooling $\mathrm{N_2 + 3H_2 \rightleftharpoons 2NH_3}$, forward reaction exothermic

1. Identify which direction is exothermic: forward.
2. Cooling favours the exothermic direction (heating favours the endothermic one).
3. Equilibrium shifts right, so the yield of ammonia increases.

What are the steps to predict the effect of a pressure increase on the position of equilibrium?

e.g. $\mathrm{N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)}$

1. Count moles of gas each side: 4 on the left, 2 on the right.
2. Increasing pressure shifts equilibrium to the side with fewer moles of gas.
3. Equilibrium shifts right, so the yield of ammonia increases.

What happens to the position of equilibrium if the concentration of a reactant is increased?

It shifts to the right (towards the products), so more product is formed.

What happens to the position of equilibrium if a product is removed as it forms?

It shifts to the right, making more product.

True or false? Increasing the pressure always increases the yield of product in a gaseous equilibrium.

False. It only shifts the equilibrium towards the side with fewer moles of gas; if both sides have equal moles there is no change.

True or false? Adding a catalyst increases the equilibrium yield of a reversible reaction.

False. The yield is unchanged; a catalyst only affects how quickly equilibrium is reached.

In $\mathrm{H_2(g) + I_2(g) \rightleftharpoons 2HI(g)}$ (iodine purple, HI colourless), what is observed if the equilibrium shifts to the right?

The colour becomes paler/fades, because there is less iodine.

What happens to the position of an equilibrium when the temperature is raised?

It shifts in the endothermic direction.