What salt is formed by the interaction of 8 g of sodium hydroxide and 19.6 g of phosphoric acid? Find its mass.

Let’s compare the amounts of reactants.

The amount of NaOH substance:

v (NaOH) = m (NaOH) / M (NaOH) = 8/40 = 0.2 (mol).

Amount of H3PO4 substance:

v (H3PO4) = m (H3PO4) / M (H3PO4) = 19.6 / 98 = 0.2 (mol).

As can be seen, 0.2 mol of H3PO4 was taken for 0.2 mol of NaOH, i.e. there would be 1 mol of H3PO4 per mole of NaOH. This ratio of reagents corresponds to the reaction equation:

NaOH + H3PO4 = NaH2PO4 + H2O

According to the reaction equation, 1 mol of NaH2PO4 is formed per 1 mol of H3PO4, therefore:

v (NaH2PO4) = v (H3PO4) = 0.2 (mol).

Thus, the mass of the formed sodium dihydrogen phosphate salt is:

m (NaH2PO4) = v (NaH2PO4) * M (NaH2PO4) = 0.2 * 120 = 24 (g).

Answer: 24 g.