Final answer:
The rate constant (k) for a reaction is calculated by determining the rate law expression and inserting the known concentrations and reaction rates from an experimental trial to solve for k. The units for k must balance the equation so that the resulting rate is in terms of mol/L/s. For temperature dependent rate constants, the Arrhenius equation is used, given the activation energy and a known rate constant.
Step-by-step explanation:
To determine the rate constant (k) for a chemical reaction, it is necessary to first establish the rate law expression by studying how the rate of the reaction depends on the concentration of the reactants. Once the rate law is determined, the value of k can be calculated by inputting the concentrations and the rate from an experimental trial into the rate law equation and solving for k.
For example, if we have data from a trial with specified concentrations and a measured reaction rate, we use these values to solve for k. If the rate law expression we derived is rate = k[A][B], and we were given a rate and concentrations for A and B, we would substitute these into the equation and solve for the rate constant k, ensuring we include the correct units which balance the equation dimensions (e.g., mol/L/s for rate and mol-2 L2/s for k when concentration units are in mol/L).
When considering changes in temperature, one would apply the Arrhenius equation to find the new rate constant at a different temperature given the activation energy and a known rate constant at a specific temperature.