Calculate `[H_3O^+],[OH^-]` and pH of a 0.2 M solution of HCN `(K_a=7.2xx10^(-10))` .

Explanation

To calculate the concentrations of \([H_3O^+]\), \([OH^-]\), and the pH of a 0.2 M solution of HCN (where \(K_a = 7.2 \times 10^{-10}\)), we can follow these steps:

### Step 1: Write the dissociation equation
The dissociation of HCN in water can be represented as:
\[ \text{HCN} \rightleftharpoons \text{H}^+ + \text{CN}^- \]
In aqueous solution, \(\text{H}^+\) can be represented as \([H_3O^+]\).
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