Rate equation and rate constant

Rate Equation and Rate Constant

The rate equation, also known as the rate law, expresses the relationship between the rate of a chemical reaction and the concentration of its reactants. It is a fundamental concept in chemical kinetics and is widely tested in exams like JEE Main.

Rate Equation (Rate Law)

The general form of a rate equation is:

Rate = k [A]^x [B]^y

Here:

• Rate is the rate of the reaction.
• k is the rate constant.
• [A] and [B] are concentrations of reactants.
• x and y are the order of the reaction with respect to A and B.

Rate Constant (k)

The rate constant serves as a proportional factor connecting the reaction rate with the concentrations of the reactants. It is specific to a particular reaction at a given temperature.

• The units of the rate constant vary depending on the overall order of the reaction.
• For a first-order reaction, units of k are \(s^{-1}\).
• For a second-order reaction, units of k are \(L·{mol}^{-1}·s^{-1}\).

Order of a Reaction

The overall order of a reaction is the sum of the powers of the concentration terms in the rate law (i.e., x + y). It is determined experimentally.

Significance of Rate Equation

• Helps predict how the rate will change with changes in concentration.
• Aids in determining reaction mechanisms.
• Useful in designing industrial chemical processes.