Table of contents

This is an oxidation-reduction (redox) reaction:

2 Br-I - 2 e- → 2 Br0 (oxidation)

2 HI + 2 e- → 2 H0 (reduction)

CaBr2 is a reducing agent, H2O is an oxidizing agent.

Word equation

  calcium bromide + water → hydrogen + calcium hydroxide + bromine

Input interpretation

CaBr2 + H2O → H2 + Ca(OH)2 + Br2

Calcium water hydrogen calcium bromine

Bromide hydroxide

Balanced equation

Balance the chemical equation algebraically: 

CaBr2 + H2O → H2 + Ca(OH)2 + Br2

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

CaBr2 + H2O → H2 + Ca(OH)2 + Br2

Set the number of atoms in the reactants equal to the number of atoms in the products for Br, Ca, H and O:

Br: 2c1 = 2cs

Ca: c1 = c4

H: 2c2 = 2c3 + 2c4

O: c2 = 2c4

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=2

c3=1 c4=1


Substitute the coefficients into the chemical reaction to obtain the balanced equation:


CaBr2 + H2O → H2 + Ca(OH)2 + Br2