Created By : Rina Nayak

Reviewed By : Rajashekhar Valipishetty

Last Updated : Apr 03, 2023

Utilise this free Rate Constant Calculator to find the rate of the reaction, half-life and rate constant easily. It will accept the rate constant, order of the reaction, and concentration of the substance as inputs and gives the rate reaction, half-life as output in the blink of an eye.

Reaction constant (k)
Concentration [A]
Reaction rate
Half life (T½)

Steps to Find Rate of the Reaction

Following are the steps to calculate the rate of reaction, the half-life of a substance effortlessly.

  • Check the order reaction, reaction constant and concentration of the substance
  • If the order reaction is zero, then the reaction rate is the rate constant.
  • If the order of the reaction is 1, then the rate of the reaction is a product of constant and concentration.
  • If the order reaction is 2, then multiply the rate constant with the square of concentration to get the reaction rate.

What is Rate Constant of Reaction | Rate of Reaction

Reaction Rate: The rate of reaction is nothing but the speed of the reaction. It tells how many moles react per liter of substance in one second. The units are M/sec, M/min or mol/(sec * L).

Rate Constant: It is the proportionality coefficient that depends on the temperature and the type of reaction. It can be described in many different equations.

Half Life: It is the period in which one half of the substrate will undergo the chemical transformation.

Rate Constant equation?

The rate constant will have different formulas based on the order reaction.

In zero order reaction,

  1. Rate constant k = reaction rate
  2. Half life T½ = [A]/2k

For first order reaction,

  1. Rate of reaction = k x [A]
  2. Half life T½ = (0.693)/k
  3. Reaction constant k = reaction rate/[A]

Second order reaction,

  1. Reaction rate = k x [A]2
  2. Half life T½ = 1/(k x [A])
  3. Rate constant k = reaction rate/[A]2


[A] is the concentration of the substance

k is the rate constant

T½ is the half life


Question: Find the reaction rate constant of a substance. If the reaction rate is 5 M/sec, concentration is 10 M and the first order reaction.


Given that

The order of reaction is first order

Reaction rate = 5 M/sec

Concentration of the substance [A] = 10 M

Rate constant k = rate/[A]

= 5/10 = 0.5 sec-1

Half life = 0.693/k

= 0.693/0.5

= 1.386 sec

The reaction rate constant is 0.5 1/sec and half life is 1.386 sec.

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FAQ’s on Rate Constant Calculator

1. What is the rate constant?

The rate constant is defined as the proportionality constant that explains the relationship between the molar concentration of the reactants ad the chemical reaction rate. It is also known as the reaction rate constant and it is dependant on the temperature.

2. How to find the rate constant?

To calculate the rate constant, you have to get the order of reaction and concentration details. For a zero-order of reaction, the reaction constant is equal to the reaction rate. For the first order of reaction, the constant rate is obtained by dividing the rate by the concentration.

3. What is the rate of reaction equation?

The reaction rate formulas for three different order of reactions is mentioned-here:

  • For zero reaction order, rate constant k = reaction rate
  • For First order rate constant k = reaction rate/concentration
  • For second order rate constant k = rate of reaction/(concentration)²

4. What are the differences between the rate of the reaction and the rate constant?

The reaction rate is expressed in terms of consumption of reactants or product formation per unit time. The rate constant is the proportionality constant in a different form. The unit of rate of reaction is mol/L cm. Rate constant unit varies based on the order of the reaction.

Rate Constant Calculator