A solution contains 0.50 mol of HCl. How much NaOH is needed to neutralize it exactly?

A solution contains 0.50 mol of HCl. How much NaOH is needed to neutralize it exactly?

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

Answer: (A)

Neutralization in this pair happens with a 1:1 mole ratio: one mole of NaOH reacts with one mole of HCl. That means the amount of base needed to completely neutralize the acid equals the amount of acid present. You have 0.50 mole of HCl, so you need 0.50 mole of NaOH to reach the equivalence point where all the acid is consumed and just enough base is present to balance it. Choosing more NaOH would leave excess base, while too little would leave some acid unreacted. Therefore, 0.50 mole of NaOH is the exact amount required.

Neutralization in this pair happens with a 1:1 mole ratio: one mole of NaOH reacts with one mole of HCl. That means the amount of base needed to completely neutralize the acid equals the amount of acid present. You have 0.50 mole of HCl, so you need 0.50 mole of NaOH to reach the equivalence point where all the acid is consumed and just enough base is present to balance it.

Choosing more NaOH would leave excess base, while too little would leave some acid unreacted. Therefore, 0.50 mole of NaOH is the exact amount required.