Which of the following statements about the rate constant (k) in a chemical reaction is true?

• A. The rate constant is affected by the initial amount of product.
• B. The rate constant depends only on the concentration of reactants.
• C. The rate constant is always the same for all reactions at any temperature.
• D. The rate constant changes with temperature.

Answer: (D)

Verified step by step guidance

1. Understand that the rate constant, denoted as \(k\), is a fundamental parameter in the rate law of a chemical reaction, which relates the reaction rate to the concentrations of reactants.
2. Recall that the rate constant \(k\) is independent of the concentrations of reactants or products; it is a constant for a given reaction at a specific temperature.
3. Recognize that the rate constant is not affected by the initial amount of product because reaction rates depend on reactant concentrations and conditions, not on how much product is present initially.
4. Know that the rate constant varies with temperature according to the Arrhenius equation: \[k = A e^{-\frac{E_a}{RT}}\] where \(A\) is the frequency factor, \(E_a\) is the activation energy, \(R\) is the gas constant, and \(T\) is the temperature in Kelvin.
5. Conclude that since \(k\) depends exponentially on temperature, changing the temperature will change the rate constant, making the statement 'The rate constant changes with temperature' true.