0.2 M solution of `Ba(OH)_2` is found to be 90% ionised at `25^@C`. Find the pH of the solution at that temperature.

Explanation

To find the pH of a 0.2 M solution of Ba(OH)₂ that is 90% ionized at 25°C, we can follow these steps:

### Step 1: Determine the ionization of Ba(OH)₂
Barium hydroxide, Ba(OH)₂, dissociates in water according to the following reaction:
\[ \text{Ba(OH)}_2 \rightarrow \text{Ba}^{2+} + 2 \text{OH}^- \]

### Step 2: Calculate the concentration of hydroxide ions
Given that the initial concentration of Ba(OH)₂ is 0.2 M and it is 90% ionized, we can calculate the concentration of hydroxide ions produced.
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