Question

Which reaction occurs when hydrogen ions react with hydroxide ions to form water?

Answer 1

Answer: D. neutralization

Explanation:

1. Substitution reaction is defined as the reaction in which one atom replaces the other atom from the compound.

$AB+C\rightarrow AC+B$

2. Saponification is a reaction in which fatty acids are made to react with alkalis to form sodium salt of fatty acids called as soaps.

3. Ionization is a type of chemical reaction in which a substance ionizes when dissolved in water.

$AB\rightarrow A^++B^-$

4. Neutralization is a type of chemical reaction in which an acid reacts with base to produce salt and water.

$BOH+HX\rightarrow BX+H_2O$

Answer 2

The answer is D. This one is a bit tricky because it requires you to realize that H+ and OH- are, respectively, an acid and a base. That's why it's neutralization.