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

What is the result of mixing an acid and an alkali?

1. Produces salt and hydrogen

2. Produces salt and carbon dioxide

3. Produces salt and water

4. Produces water and oxygen

The correct answer is: Produces salt and water

Mixing an acid and an alkali typically results in a neutralization reaction, which produces salt and water. In this process, the acid donates hydrogen ions (H⁺) and the alkali donates hydroxide ions (OH⁻). When these ions combine, they form water (H₂O). The remaining components, from the acid and the alkali, combine to form a salt. For example, when hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), the reaction produces sodium chloride (NaCl), which is table salt, and water. This demonstrates the general principle of acid-base reactions where the formation of salt and water occurs as end products. The other options listed do not accurately represent the primary products formed in a typical acid-alkali reaction. While some acids and carbonates can produce carbon dioxide, that is a different reaction altogether and does not occur in the standard acid-alkali neutralization. Similarly, reactions involving oxygen are not characteristic of acid-alkali interactions. Thus, the correct result of mixing an acid and an alkali is indeed the production of salt and water.