Which of the following statements is incorrect ?

Options

A. In equilibrium mixture of ice and water kept in perfectly insulated flask, amss of ice and water does not change with time.
B. The intensity of red colour increase when oxalic acid is added to a solution containing iron (III) nitrate and potassium thiocyanate.
C. On addition of catalyst, the equilibrium constant value is not affected.
D. Equilibroum constant for a reaction with negative `DeltaH` value decreases as the temperature increases.

Explanation

To determine which statement is incorrect, let's analyze each statement step by step.

### Step 1: Analyze Statement A
**Statement A:** "In an equilibrium mixture of ice and water kept in a perfectly insulated flask, the mass of ice and water does not change with time."

- **Explanation:** At equilibrium, the system is stable, meaning that the amounts of reactants and products remain constant over time. Since the flask is insulated, there is no heat exchange with the environment, and the temperature remains constant. Therefore, the mass of ice and water will not change.
- **Conclusion:** This statement is **true**.

### Step 2: Analyze Statement B
**Statement B:** "The intensity of red color increases when oxalic acid is added to a solution containing iron(III) nitrate and potassium thiocyanate."

- **Explanation:** When oxalic acid (H2C2O4) is added to a solution containing Fe³⁺ ions and SCN⁻ ions, it reacts with Fe³⁺ to form a stable complex, which reduces the concentration of Fe³⁺ ions. According to Le Chatelier's principle, if the concentration of a reactant decreases, the equilibrium will shift to the left to compensate, resulting in a decrease in the formation of the red complex (Fe(SCN)²⁺). Thus, the intensity of the red color will decrease, not increase.
- **Conclusion:** This statement is **incorrect**.

### Step 3: Analyze Statement C
**Statement C:** "On adding a catalyst, the equilibrium constant value is not affected."

- **Explanation:** A catalyst speeds up the rate of both the forward and reverse reactions equally, allowing the system to reach equilibrium faster. However, it does not change the position of equilibrium or the equilibrium constant (Kc), which is only affected by temperature.
- **Conclusion:** This statement is **true**.

### Step 4: Analyze Statement D
**Statement D:** "The equilibrium constant for a reaction with a negative ΔH value decreases as temperature increases."

- **Explanation:** For exothermic reactions (negative ΔH), increasing the temperature shifts the equilibrium to the left (towards the reactants) to absorb the added heat. This results in a decrease in the equilibrium constant (Kc). Therefore, this statement is correct.
- **Conclusion:** This statement is **true**.

### Final Conclusion
Based on the analysis:
- Statement A: True
- Statement B: **Incorrect** (this is our answer)
- Statement C: True
- Statement D: True

Thus, the incorrect statement is **B**.

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