The rate constant of a reaction depends on:

Temperature

The rate constant (k) is a proportionality constant that relates the rate of a reaction to the concentrations of the reactants. It is determined experimentally and is specific to a particular reaction at a given temperature.

The temperature has a significant influence on the rate constant. Generally, as the temperature increases, the rate constant also increases. This relationship is described by the Arrhenius equation, which states that the rate constant is exponentially proportional to the temperature:

\(k = Ae^{(-Ea/RT)}\)

In this equation, Ea is the activation energy, R is the gas constant, and T is the absolute temperature. The exponential term \(e^{(-Ea/RT)}\) reflects the temperature dependence of the rate constant.

Therefore, the correct answer is (3) Temperature.