What effect does a decrease in temperature have on the overall rate of a chemical reaction?

• A. It decreases the rate of the reaction.
• B. It causes the reaction to reach equilibrium faster.
• C. It has no effect on the rate of the reaction.
• D. It increases the rate of the reaction.

Answer: (A)

Verified step by step guidance

1. Understand that the rate of a chemical reaction depends on the frequency and energy of collisions between reactant molecules.
2. Recall the Arrhenius equation, which relates the rate constant \(k\) to temperature \(T\): \[k = A e^{-\frac{E_a}{RT}}\] where \(A\) is the frequency factor, \(E_a\) is the activation energy, \(R\) is the gas constant, and \(T\) is the temperature in Kelvin.
3. Recognize that decreasing the temperature \(T\) increases the value of \(\frac{E_a}{RT}\), making the exponential term smaller, which decreases the rate constant \(k\).
4. Since the rate of reaction is proportional to the rate constant \(k\), a decrease in temperature leads to a decrease in the overall reaction rate.
5. Note that while temperature affects the rate at which equilibrium is reached, it does not change the position of equilibrium itself unless the reaction is endothermic or exothermic.