Question

Statement A: pH of buffer increases with increasing temperature.
Statement B: The value of \(K_w\) of water decreases with decreasing temperature.

• A. A is correct, but B is wrong
• B. Both A and B are correct
• C. Both A and B are wrong
• D. A is wrong but B is correct

Hint:

Remember that the ionization of water is an endothermic process. Therefore: \[ \text{Temperature} \uparrow \Rightarrow K_w \uparrow \] and \[ \text{Temperature} \downarrow \Rightarrow K_w \downarrow \] This is an important concept in ionic equilibrium and buffer chemistry.

Answer 1

The Correct Option is B

Step 1: Analyze Statement A.
The pH of a buffer solution depends on the dissociation constant of the weak acid/base present in the buffer. According to the Henderson-Hasselbalch equation, \[ pH=pK_a+\log\frac{[\text{Salt}]}{[\text{Acid}]} \] The value of \(pK_a\) changes with temperature. For many buffer systems, an increase in temperature causes a change in dissociation equilibrium, leading to an increase in pH.
Therefore, Statement A is considered correct.

Step 2: Analyze Statement B.
The ionic product of water is \[ K_w=[H^+][OH^-] \] The ionization of water is an endothermic process: \[ H_2O \rightleftharpoons H^+ + OH^- \] Since the reaction is endothermic, increasing temperature increases \(K_w\), while decreasing temperature decreases \(K_w\).
Hence, \[ K_w \downarrow \quad \text{when temperature} \downarrow \] Therefore, Statement B is correct.

Step 3: Verify both statements together.
Statement A is correct according to the behavior of buffer systems with temperature.
Statement B is also correct because the ionic product of water decreases on lowering temperature.

Step 4: Match with the given options.
Since both statements are correct, the appropriate choice is: Both A and B are correct

Step 5: Final conclusion.
Hence, \[ \boxed{\text{Both A and B are correct}} \] Therefore, option (2) is the correct answer.