Question

Give the unit rate constant of a reaction.

Answer 1

Rate constant also known by the name proportionality constant which gives the relationship between molar concentration of the reactants and chemical reaction. This is generally denoted by the symbol K.

Complete answer:
Rate constant can be easily calculated with the help of Arrhenius equation. This equation gives us the formula for the temperature dependence of reaction rates. The Arrhenius equation has many applications but the main and very important application of the Arrhenius equation is it is useful in determination of rate of chemical reaction and for the calculation of energy of activation.
Unit of rate constant also depends on the order of reaction where order of reaction can be defined as the Sum of the exponents which gives us the overall order of a reaction. The order of a complex reaction is given by the order of the slowest step in the sequence of various steps involved in that reaction.
Hence unit of rate constant for various order of reactions can be defined as follows:
Zero order reaction = $mol{{L}^{-1}}{{\sec }^{-1}}$
First order reaction = ${{\sec }^{-1}}$
Second order reaction = ${{M}^{-1}}{{\sec }^{-1}}$
Third order reaction = ${{M}^{-2}}{{\sec }^{-1}}$
Hence in this way we can assign units of rate constant for various orders of reaction.

Note:
The Order of reaction tells the relationship between the rate of a chemical reaction and the concentration of the species taking part in it. In order to calculate the reaction order the rate expression of the reaction is very necessary.