if 75.0 ml of 1.5m sodium hydroxide reacts with 100.0 ml of 2.0m phosphoric acid, to give sodium phosphate and water, how many grams of Na3Po4 may be produced?

Answer 1

First, I will assume you meant 1.5 M and 2.0 M. M stands for molarity, m stands for molality. Second, this is a limiting reagent problem and you know that because amounts are given for BOTH reactants.

3NaOH + H3PO4 ==> Na3PO4 + 3H2O

mols NaOH = M x L = ?
mols H3PO4 = M x L = ?

Using the coefficients in the balanced equation, convert mols NaOH to mols of the product.
Do the same and convert mols H3PO4 to mols of the product.
It is likely that these two values will not be the same; the correct value will ALWAYS be the smaller of the two and the reagent responsible for that will be the limiting reagent.

Using the smaller value for mols of the product, convert to grams. g Na3PO4 = mols Na3PO4 x molar mass Na3PO4 = ?.