According to Le Chatelier's principle, what happens to the position of equilibrium when a system at equilibrium is subjected to a decrease in temperature for an exothermic reaction?

• A. It shifts toward the reactants.
• B. It shifts to a higher pressure.
• C. It shifts toward the products (the exothermic direction) to produce heat.
• D. It remains unchanged.

Answer: (C)

A system at equilibrium adjusts to counteract disturbances. For an exothermic reaction, heat is produced on the product side. When the temperature is lowered, heat is removed from the system, so the equilibrium shifts in the direction that generates heat to counteract that loss. That means it moves toward the products, the exothermic direction, producing more heat. This is why the correct outcome is a shift toward the products. Shifting toward reactants would require absorbing heat (the endothermic direction), which isn’t favored when temperature decreases. The system won’t remain unchanged because a temperature change prompts a shift to oppose it.