Table of contents

This is an oxidation-reduction (redox) reaction:

Al0 - 2 e- → AlII (oxidation)

2 NIII - 4 e- → 2 NV (oxidation)

CrVI + 6 e- → Cr0 (reduction)

Al is a reducing agent, Cr(NO3)2 is a reducing agent, Cr(NO3)2 is an oxidizing agent.

Input interpretation

Cr(NO3)2 + Al → Al(NO3)2 + Cr

Aluminum chromium

Balanced equation

Balance the chemical equation algebraically:

Cr(NO3)2 + Al → Al(NO3)2 + Cr

Add stoichiometric coefficients, c1, to the reactants and products:

c1Cr(NO3)2 + c2Al → c3Al(NO3)2 + c4Cr

Set the number of atoms in the reactants equal to the number of atoms in the products for Cr, N, O and Al:

Cr: c1 = c4

N: 2c1 = 2c3

0: 6c1 = 6c3 

Al: c2 = c3

Since the coefficients are relative quantities and underdetermined, choose a coefficient to set arbitrarily. To keep the coefficients small, the arbitrary value is ordinarily one. For instance, set c1 = 1 and solve the system of equations for the remaining coefficients:

c1 = 1 

c2 = 1

c3 = 1 

c4 = 1

Substitute the coefficients into the chemical reaction to obtain the balanced



Cr(NO3)2 + Al → Al(NO3)2 + Cr