Calculate the pH of the solution in which `0.2 M NH_(4)Cl` and `0.1 M NH_(3)` are present. The `pK_(b)` of ammonia solution is `4.75`.

Explanation

To calculate the pH of a solution containing 0.2 M NH₄Cl and 0.1 M NH₃, we can follow these steps:

### Step 1: Identify the relevant equilibrium reaction
The equilibrium reaction for ammonia (NH₃) in water is:
\[ \text{NH}_3 + \text{H}_2\text{O} \rightleftharpoons \text{NH}_4^+ + \text{OH}^- \]

### Step 2: Set up the initial concentrations
Given:
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