Question

pH of a buffer containing 6.0 g of \(CH_3 COOH\) and 8.2 g of \(CH_3 COONa\) in 1 L of water is ($p{K}_a$ = 4.5)

• A. 7.5
• B. 4.5
• C. 5.5
• D. 6.5

Answer 1

The correct option is B

4.5

[$C{H}_{3}COOH$] = $\frac{6.0}{60}\times 1$ = 0.1 M

[$C{H}_{3}COONa$] = $\frac{8.2}{82}\times 1$ = 0.1 M

So pH = $p{K}_a$ + log$\frac{\left[Salt\right]}{\left[Acid\right]}$

Or pH = 4.5 + log$\frac{0.1}{0.1}$ = 4.5