How can altering the temperature change the yield in a reversible reaction?

Altering the temperature can change the yield in a reversible reaction by shifting the position of the equilibrium.

In a reversible reaction, both the forward and backward reactions occur simultaneously. The rate at which these reactions occur can be influenced by several factors, one of which is temperature. According to Le Chatelier's principle, if a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium moves to counteract the change.

When the temperature is increased, the system will try to decrease it by favouring the reaction that absorbs heat, which is the endothermic reaction. This will increase the yield of the products of the endothermic reaction. Conversely, if the temperature is decreased, the system will try to increase it by favouring the exothermic reaction, which releases heat. This will increase the yield of the products of the exothermic reaction.

For example, consider the reversible reaction of nitrogen and hydrogen to form ammonia. This reaction is exothermic in the forward direction (forming ammonia), and endothermic in the reverse direction (breaking down ammonia). If the temperature is increased, the position of equilibrium will shift to the left, favouring the endothermic reaction and decreasing the yield of ammonia. If the temperature is decreased, the position of equilibrium will shift to the right, favouring the exothermic reaction and increasing the yield of ammonia.

In summary, altering the temperature can change the yield in a reversible reaction by shifting the position of equilibrium in a direction that counteracts the change in temperature. This is a direct application of Le Chatelier's principle, which is a fundamental concept in the study of chemical equilibria. Understanding this principle and how it applies to temperature changes can help you predict the effect of such changes on the yield of a reversible reaction.