A buffer solution contains equal concentrations of weak acid and its salt with strong base. Calculate pH of…

A buffer solution contains equal concentrations of weak acid and its salt with strong base. Calculate pH of buffer solution if dissociation constant of weak acid is $1.8 \times 10^{-5}$.
  1. 4.7447
  2. 5.1420
  3. 5.8496
  4. 4.0128

Solution

For an acidic buffer, $\begin{array}{ll} \therefore & \mathrm{pH}=\mathrm{pK}_{\mathrm{a}}+\log \frac{[\text { Salt }]}{[\text { Acid }]} \\ & (\because[\text { Salt }]=[\text { Acid }]) \\ \therefore \quad & \mathrm{pH}=\mathrm{pK}_{\mathrm{a}}=-\log \mathrm{K}_{\mathrm{a}}=-\log \left(1.8 \times 10^{-5}\right) \\ \therefore \quad & \mathrm{pH}=-[\log 1.8-5 \log 10]=4.7447 \end{array}$

Asked in: MHT CET 2024 (10 May Shift 2)

Practice more Ionic Equilibria questions on Aicharya