Which parameter is constant for a given temperature in rate law rate = k[A]^m?

Which parameter is constant for a given temperature in rate law rate = k[A]^m?

• A. [A]
• B. m
• C. k
• D. [A]^m

Answer: (C)

In a rate law, the temperature affects the rate through the rate constant, k. For a given temperature, k stays fixed, so the entire temperature dependence is contained in k and does not change as the reaction proceeds. The concentration [A] is the actual amount of reactant present at a moment and it changes as the reaction occurs, so it is not constant. The exponent m is the reaction order with respect to A, a fixed property of the mechanism, but what matters for how the rate responds at that temperature is that k remains constant when T is fixed. Therefore, the parameter that stays constant at a given temperature is the rate constant, k.

In a rate law, the temperature affects the rate through the rate constant, k. For a given temperature, k stays fixed, so the entire temperature dependence is contained in k and does not change as the reaction proceeds. The concentration [A] is the actual amount of reactant present at a moment and it changes as the reaction occurs, so it is not constant. The exponent m is the reaction order with respect to A, a fixed property of the mechanism, but what matters for how the rate responds at that temperature is that k remains constant when T is fixed. Therefore, the parameter that stays constant at a given temperature is the rate constant, k.