Bases when dissolved in water produce ________________.

When bases are dissolved in water, they produce **hydroxide ions (OH⁻)**.

Here's an explanation of how this works:

1. **Definition of a Base**: In chemistry, a base is a substance that can accept hydrogen ions (H⁺) or donate a pair of electrons.

2. **Dissolution in Water**: When a base dissolves in water, it dissociates into its constituent ions.

3. **Formation of Hydroxide Ions**: For many bases, especially those that are strong or soluble in water, they dissociate to produce hydroxide ions (OH⁻).

For example, sodium hydroxide (NaOH) is a common base. When it dissolves in water, it dissociates as follows:
\[ \text{NaOH} \rightarrow \text{Na}^+ + \text{OH}^- \]

4. **Effect on pH**: The increase in hydroxide ions makes the solution basic (alkaline), which is reflected in a higher pH value.

In summary, bases produce hydroxide ions (OH⁻) when dissolved in water.