Why does a low temperature increase the yield of ammonia?

The correct answer highlights the principle of Le Chatelier's principle in chemistry, which states that if a system at equilibrium is subjected to a change in temperature, pressure, or concentration, the equilibrium will shift in a direction that counteracts the change.

In this context, the formation of ammonia from nitrogen and hydrogen is an exothermic reaction, meaning it releases heat. When the temperature is lowered, the equilibrium shifts towards the products (in this case, ammonia) in order to increase the temperature and counteract the change. This results in an increase in the yield of ammonia, as the system favors the formation of products that release heat.

In comparison, the other options address different aspects of the reaction dynamics but do not directly correlate with the principle governing the yield change with temperature fluctuations. For instance, while a reaction might occur faster at certain temperatures, that does not specifically account for the changes in ammonia production related to the reaction's exothermic nature.