When aqueous solutions of phosphoric acid (H3PO4) and sodium hydroxide (NaOH) are mixed together, the products of the reaction are sodium phosphate salts and water. The specific products formed depend on the stoichiometric ratio of phosphoric acid and sodium hydroxide used in the reaction.

1. Formation of Sodium Dihydrogen Phosphate (NaH2PO4):

If one mole of phosphoric acid is reacted with one mole of sodium hydroxide, the product is sodium dihydrogen phosphate. The reaction can be represented as:

H3PO4 + NaOH → NaH2PO4 + H2O

In this reaction, one hydrogen ion (H+) from phosphoric acid is replaced by one sodium ion (Na+) from sodium hydroxide, resulting in the formation of sodium dihydrogen phosphate.

2. Formation of Sodium Hydrogen Phosphate (Na2HPO4):

If two moles of sodium hydroxide are reacted with one mole of phosphoric acid, the product is sodium hydrogen phosphate. The reaction can be represented as:

H3PO4 + 2NaOH → Na2HPO4 + 2H2O

In this reaction, two hydrogen ions (H+) from phosphoric acid are replaced by two sodium ions (Na+) from sodium hydroxide, resulting in the formation of sodium hydrogen phosphate.

3. Formation of Trisodium Phosphate (Na3PO4):

If three moles of sodium hydroxide are reacted with one mole of phosphoric acid, the product is trisodium phosphate. The reaction can be represented as:

H3PO4 + 3NaOH → Na3PO4 + 3H2O

In this reaction, all three hydrogen ions (H+) from phosphoric acid are replaced by three sodium ions (Na+) from sodium hydroxide, resulting in the formation of trisodium phosphate.

Therefore, the product of mixing aqueous solutions of phosphoric acid and sodium hydroxide depends on the mole ratio of the reactants and can be sodium dihydrogen phosphate, sodium hydrogen phosphate, or trisodium phosphate.