A : At higher temperature , `K_w` of water remains unaltered.
R: `k_w` is a constant.

Options

A. If both Assertion & Reason are true and the reason in the corret explanation of the assertion, then mark
B. If both assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark
C. If Assertion is true statement but Reason is false then mark
D. If both Assertion and Reason are false statements , then mark

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided:

**Assertion (A):** At higher temperature, \( K_w \) of water remains unaltered.
**Reason (R):** \( K_w \) is a constant.

### Step 1: Understanding \( K_w \)
The ion product of water, \( K_w \), is defined as the product of the concentrations of hydrogen ions \([H^+]\) and hydroxide ions \([OH^-]\) in water at equilibrium:
\[ K_w = [H^+][OH^-] \]

### Step 2: Effect of Temperature on \( K_w \)
The dissociation of water is an endothermic reaction:
\[ H_2O \rightleftharpoons H^+ + OH^- \]
Since this reaction absorbs heat, increasing the temperature will shift the equilibrium to the right, producing more \( H^+ \) and \( OH^- \) ions.

### Step 3: Conclusion on Assertion (A)
As the temperature increases, the concentrations of \( H^+ \) and \( OH^- \) ions increase, which means \( K_w \) will also increase. Therefore, the assertion that \( K_w \) remains unaltered at higher temperatures is **false**.

### Step 4: Conclusion on Reason (R)
The reason states that \( K_w \) is a constant. However, \( K_w \) is not a constant value; it changes with temperature. For example, at 25°C, \( K_w \) is \( 1.0 \times 10^{-14} \), but at 30°C, it is \( 1.47 \times 10^{-14} \). Thus, the reason is also **false**.

### Final Conclusion
Both the assertion and the reason are false. Therefore, the correct option is that both A and R are false statements.

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