# Equilibrium Constant

**Calculator of the equilibrium constant of a chemical reaction.**

Chemical reaction :

\(\ce{aA + bB <=> cC + dD}\) where molecules A,B,C,D are the reactants and products of the reaction and a,b,c,d are the coefficients of molecules A, B, C, D.

Equilibrium constant formula : `K_c = \frac{[C]^c*[D]^d}{[A]^a*[B]^b}` [A], [B], [C], [D] are the concentrations of A, B, C and D in mol per liter.

Do not enter molecules symbols like SO2, H2 ... Enter data separated by space(s).Powers of 10 : input

**2.5*10^-3**or

**2.5e-3**for [A] = `2.5*10^(-3)` mol/l

This tool calculates the equilibrium constant for a chemical reaction.

We consider the following chemical reaction :

\(\ce{aA + bB <=> cC + dD}\)

A and B are the reactants.

C and D are the products.

a and b are the reactant coefficients.

c and d are the product coefficients.

The equilibrium constant is calculated as follows,

`K_c = \frac{[C]^c*[D]^d}{[A]^a*[B]^b}`

[A]: Molar concentration of reactant A in mol per liter (mol/l)

[B]: Molar concentration of reactant B in mol per liter (mol/l)

[C]: Molar concentration of product C in mol per liter (mol/l)

[D]: Molar concentration of product D in mol per liter (mol/l)

**Example of use**

This is the chemical reaction of ammonia synthesis:

\(\ce{N2 + 3H2 <=> 2NH3}\)

There are 2 reactants which are nitrogen and hydrogen and one product, ammonia.

Reactants:

A = `N_2`

B = `H_2`

The product:

C = `NH_3`

Coefficients:

a = 1

b = 3

c = 2

Then, the following values should be entered in the form:

- Field "Coefficients of Reactants" : 1 3

- Field "Coefficients of Products" : 2

If we suppose the equilibrium molar concentrations are (in mol/l):

[`N_2`] = 0.03

[`H_2`] = 0.09

[`NH_3`] = `1.7*10^(-8)`

Then, we should enter the following values in the calculator:

- Field "Reactant concentrations (mol/l)": 0.03 0.09

- Field "Product concentrations (mol/l)": 1.7e-8

That leads to the following calculator: `Kc = 1.32*10^(-11)`

## See also

Conversion of molar concentration units

Ionic Force Calculator

Solution and Equilibrium Calculators

Chemistry Calculators