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

What does the reaction of an acid with a base produce?

1. Salt and carbon dioxide

2. Salt and water

3. Water and hydrogen

4. Hydrogen and oxygen

The correct answer is: Salt and water

When an acid reacts with a base, the primary products of this reaction are salt and water. This type of reaction is called a neutralization reaction. The acid donates protons (H⁺ ions), while the base donates hydroxide ions (OH⁻). When these ions combine, they form water (H₂O). Additionally, the remaining ions from the acid and base combine to form a salt. For example, if hydrochloric acid (HCl) reacts with sodium hydroxide (NaOH), the products formed are sodium chloride (NaCl), which is the salt, and water. This process is fundamental to many chemical reactions and is routinely seen in various applications, including titrations in laboratory settings. The other options mentioned don't accurately represent the products of an acid-base reaction. For instance, salt and carbon dioxide can occur in certain reactions involving carbonates, but that is not a general outcome of acid-base reactions. Additionally, the production of just water and hydrogen, or hydrogen and oxygen, does not encompass the typical neutralization process, which is primarily associated with the formation of salt and water.