# Equivalent Weight of H3PO4

An equivalent weight of a solution is defined as the molecular weight of the solute divided by the valence of the solute. Equivalent weight is used for predicting the mass of a substance that reacts with one atom of hydrogen in an acid-base analysis like in titration.

The given reaction is:

Ca(OH)2 + H3PO4 → CaHPO4 + 2H2O

In the reaction,

H3PO4 → HPO42- + 2H+

2 hydrogen ions are left from the orthophosphoric acid.

Therefore, the valency factor = 2

$Equivalent weight = \frac{molecular weight}{2}$

Molecular weight calculation.

Number of H are 3

3 × 1 = 3

Number of P is 1

1 × 31 = 31

Number of O are 4

4 × 16 = 64

Molecular weight = 3 + 31 + 64

Molecular weight = 98

Therefore, the equivalent weight = (98/2) = 49

Equivalent weight of H3POis 49.