During an acid-base neutralization, how many moles of hydroxide ions will react with one mole of hydrogen ions?

During an acid-base neutralization, how many moles of hydroxide ions will react with one mole of hydrogen ions?

• A. 0.5 mol
• B. 1.0 mol
• C. 17.0 mol
• D. 22.4 mol

Answer: (B)

The key idea is that neutralization is a 1:1 proton transfer between the acid and the base. In water, the acid provides hydrogen ions (H+), and the base provides hydroxide ions (OH−). They combine directly to form water: H+ + OH− → H2O. Because this reaction consumes one hydrogen ion for every hydroxide ion, one mole of hydroxide reacts with one mole of hydrogen. That’s why the correct amount is 1.0 mole. The other numbers don’t fit the stoichiometry of this proton transfer; for example, 0.5 would imply half as much base as acid, and 17.0 or 22.4 are not related to the 1:1 relationship (22.4 L is the molar volume of gas at STP, not a factor in this aqueous reaction).

The key idea is that neutralization is a 1:1 proton transfer between the acid and the base. In water, the acid provides hydrogen ions (H+), and the base provides hydroxide ions (OH−). They combine directly to form water: H+ + OH− → H2O. Because this reaction consumes one hydrogen ion for every hydroxide ion, one mole of hydroxide reacts with one mole of hydrogen. That’s why the correct amount is 1.0 mole. The other numbers don’t fit the stoichiometry of this proton transfer; for example, 0.5 would imply half as much base as acid, and 17.0 or 22.4 are not related to the 1:1 relationship (22.4 L is the molar volume of gas at STP, not a factor in this aqueous reaction).