Rate Constant
Definition
The k in the rate law: a number capturing how inherently fast a reaction is at a given temperature. Bigger k means a faster reaction.
Symbol: ·
Technical definition
The rate constant (k) is the proportionality constant in a rate law, specific to a reaction at a given temperature. Its units vary with the overall reaction order, and its temperature dependence follows the Arrhenius equation.
Example
A first-order reaction with k = 0.05 s^-1 converts about 5 percent of the remaining reactant per second at the start.
Common confusion
The rate constant is not the reaction rate. The constant k is fixed at a given temperature, while the actual rate falls as reactant concentrations drop during the reaction.