Question

Calculate the pOH of buffer solution formed from $0.3 \text{ M}$ weak base and $0.45 \text{ M}$ of its salt with strong acid [$pK_b = 4.7447$]}

• A. 6.45
• B. 4.07
• C. 4.92
• D. 5.51

Hint:

Buffer formula: $\text{pOH} = pK_b + \log \frac{\text{salt}}{\text{base}}$

Answer 1

The Correct Option is C

Concept: For basic buffer: \[ \text{pOH} = pK_b + \log \frac{[\text{salt}]}{[\text{base}]} \]

Step 1: Substitute values. \[ \text{pOH} = 4.7447 + \log \frac{0.45}{0.3} \]

Step 2: Simplify ratio. \[ \frac{0.45}{0.3} = 1.5 \] \[ \log 1.5 \approx 0.176 \]

Step 3: Calculate pOH. \[ \text{pOH} = 4.7447 + 0.176 \approx 4.92 \]

Step 4: Conclusion.
Thus, pOH = 4.92 Final Answer: Option (C)