On increasing the temperature, the pKw

Options

A. Increase
B. Decrease
C. Remains constant
D. May increase or decrease

Answer

To solve the question regarding the effect of temperature on the value of pKw, we can follow these steps:

### Step 1: Understand the relationship between Kw and pKw
Kw is the ion product of water, which is defined as:
\[ K_w = [H^+][OH^-] \]
pKw is defined as:
\[ pK_w = -\log K_w \]

### Step 2: Analyze the effect of temperature on Kw
As temperature increases, the value of Kw also changes. For water, the ion product increases with temperature due to the endothermic nature of the dissociation of water into hydrogen ions and hydroxide ions.

### Step 3: Determine the relationship between Kw and pKw
Since pKw is the negative logarithm of Kw, if Kw increases, pKw will decrease. This is because:
\[ pK_w = -\log K_w \]
If \( K_w \) increases, the logarithm value increases, and thus the negative sign causes pKw to decrease.

### Step 4: Conclusion
Therefore, when the temperature increases, the value of pKw decreases.

### Final Answer:
On increasing the temperature, the pKw value decreases.

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