International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

In an acid-base reaction, what is the byproduct of the neutralization process?

1. Hydrogen gas

2. Carbon dioxide

3. Water

4. Salt

The correct answer is: Water

In an acid-base reaction, the byproducts of a neutralization process are water and a salt. When an acid reacts with a base, they combine to neutralize each other. The acid donates protons (H+) while the base donates hydroxide ions (OH-). When these ions combine, they form water (H2O). Additionally, the remaining ions from the acid and base form a salt. Therefore, while water is indeed a crucial byproduct of the neutralization reaction, the complete outcome includes both water and a salt. However, since the question specifically asks for a singular byproduct and highlights water, it is accurate to identify it as the main product. The other choices do not represent typical byproducts of neutralization reactions. For example, hydrogen gas is generated in reactions involving metals with acids, carbon dioxide is released in reactions involving carbonates and acids, but neither occurs in a standard acid-base neutralization. Thus, in the context of a straightforward acid-base reaction, water is indeed the primary notable byproduct that results from the combination of H+ and OH- ions.