How much water is formed when 1.0 mole of HCl reacts with 1.0 mole of NaOH?

• A. 0.50 mol
• B. 2.0 mol
• C. 0.25 mol
• D. 1.0 mol

Answer: (D)

In an acid–base neutralization, the reaction between a strong acid like HCl and a strong base like NaOH occurs in a strict 1:1 ratio to form water and a salt. The balanced equation is HCl + NaOH → NaCl + H2O, so one mole of water is produced for every mole of reaction that occurs.

Since you start with one mole of each reactant, they both react completely. That means exactly one mole of water forms. If one reactant were in excess, only the amount corresponding to the limiting reagent would become water, but with equimolar amounts you get one mole of water. The other potential amounts would require a different stoichiometry or amounts of reactants, not what this setup has.