Caculate the pH value of 0.20M solution of methyl amine `(CH_(3)NH_(2))` at 298 K, given that its ionisation constant `(K_(b))` is `4.4 xx 10^(-5).`

Explanation

To calculate the pH value of a 0.20 M solution of methyl amine (CH₃NH₂) at 298 K, given that its ionization constant (K_b) is 4.4 × 10^(-5), we can follow these steps:

### Step 1: Write the dissociation equation
Methyl amine (CH₃NH₂) is a weak base and dissociates in water as follows:
\[ \text{CH}_3\text{NH}_2 + \text{H}_2\text{O} \rightleftharpoons \text{CH}_3\text{NH}_3^+ + \text{OH}^- \]

### Step 2: Set up the initial concentrations
At the start (t = 0), the concentration of CH₃NH₂ is 0.20 M, and the concentrations of CH₃NH₃⁺ and OH⁻ are both 0:
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