Which of the following is an acid-base neutralization reaction?

• A. NaOH + HCl -> NaCl + H2O
• B. H2SO4 + NaOH -> Na2SO4 + H2O
• C. NaCl + H2O -> NaOH + HCl
• D. CO2 + H2O -> H2CO3

Answer: (A)

Acid-base neutralization happens when an acid donates a proton to a base, producing water and a salt. The classic example shows the base providing OH− and the acid providing H+, which combine to form water, while the remaining ions form a salt.

The reaction of sodium hydroxide with hydrochloric acid is the clearest illustration: NaOH plus HCl yields NaCl and H2O. This is a straightforward, balanced representation of neutralization: the water molecule comes from the H+ and OH−, and the salt comes from the other ions, Na+ and Cl−.

Other options either aren’t balanced as written or don’t depict the same clean proton-transfer process. For sulfuric acid and sodium hydroxide, the neutralization still occurs, but the correct balanced form is H2SO4 + 2 NaOH -> Na2SO4 + 2 H2O. One choice effectively reverses a neutralization, and another option shows CO2 reacting with water to form carbonic acid, which is hydration/solvation rather than a proton-transfer neutralization.