Table of contents

This is an oxidation-reduction (redox) reaction:

6 HI + 6 e- → 6 H0 (reduction)

3 Fe0 - 6 e- → 3 FeII (oxidation)

H3PO4 is an oxidizing agent, Fe is a reducing agent.

Input interpretation

Fe + H3PO4 → Fe3(PO4)2 + H2

Iron phosphoric acid hydrogen

Balanced equation

Balance the chemical equation algebraically:

Fe + H3PO4 → Fe3(PO4)2 + H2

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

c1Fe + c2H3PO4 → c3 Fe3(PO4)2 + c4H2

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

Fe: C1 = 3c3

H: 3c2=2c4

 O: 4c2=8c3

 P: c2 = 2c3

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 c3 = 1 and solve the system of equations for the remaining coefficients:

C1 = 3 C2=2

C3 = 1 C4=3

Substitute the coefficients into the chemical reaction to obtain the balanced



Fe + H3PO4 → Fe3(PO4)2 + H2