In a buffer solution containing equal concentration of $ B^- $ and HB, the $ K_b $ for $ B^- $ is $ 10^{-10} $ . The pH of buffer solution is

Question

Phenol does not undergo nucleophilic substitution reaction easily due to:

Answer 1

To determine the pH of the buffer solution, we need to use the relationship between the base dissociation constant ($ K_b $) and the pH of a buffer solution where the concentrations of the conjugate base ($ B^- $) and its conjugate acid (HB) are equal.

The relationship is given by the following equation for a buffer:

pH = 14 - pOH

First, we calculate the $ pOH $ using $ K_b $ since it's a base.

Given: K_b = 10^{-10}

In a buffer solution where the concentration of base and its conjugate acid are equal, the pOH can be found using:

pOH = -\log K_b = -\log (10^{-10}) = 10

Now, calculate the pH:

pH = 14 - pOH = 14 - 10 = 4

Thus, the pH of the buffer solution is 4.

To justify the correct option and rule out others:

Option 10: This would imply that the $ pOH $ is 4, contradicting the calculated $ pOH = 10 $.
Option 7: This is neutral pH for pure water, not a valid result for this buffer solution.
Option 6: This would give a $ pOH $ of 8, which does not align with $ K_b = 10^{-10} $.
Option 4: Correctly reflects the calculation $ pH = 4 $.

Therefore, the correct answer is 4.

Answer 2