Seema told Rohan that water is a compound, not an element and to justify it, she gave the following reasons : I. Heat and light are given out during its formation from its constituent elements. II. It contains hydrogen and oxygen in the ratio of 1:8 by mass. III. Its boiling point is 373 K under one atmospheric pressure. The correct reasons are

Options

A. I and II only
B. II and III only
C. I and III only
D. I, II and III

Explanation

To determine whether Seema's reasons for classifying water as a compound are correct, we need to analyze each reason she provided:

### Step 1: Analyze the First Reason
**Statement:** Heat and light are given out during its formation from its constituent elements.

**Explanation:** When hydrogen gas (H₂) reacts with oxygen gas (O₂) to form water (H₂O), this reaction is exothermic, meaning it releases heat and light. This is a characteristic of compound formation.

**Conclusion:** The first reason is correct.

### Step 2: Analyze the Second Reason
**Statement:** It contains hydrogen and oxygen in the ratio of 1:8 by mass.

**Explanation:** The molecular formula for water is H₂O. In one molecule of water, there are 2 hydrogen atoms and 1 oxygen atom. The atomic mass of hydrogen is approximately 1 g/mol, and that of oxygen is approximately 16 g/mol. Therefore, the mass ratio of hydrogen to oxygen is calculated as follows:
- Mass of 2 hydrogen atoms = 2 × 1 = 2 g
- Mass of 1 oxygen atom = 16 g
- Ratio of hydrogen to oxygen = 2:16 = 1:8

**Conclusion:** The second reason is also correct.

### Step 3: Analyze the Third Reason
**Statement:** Its boiling point is 373 K under one atmospheric pressure.

**Explanation:** The boiling point of water at standard atmospheric pressure (1 atm) is 100 °C. To convert this to Kelvin, we add 273:
- 100 °C + 273 = 373 K

**Conclusion:** The third reason is correct.

### Final Conclusion
All three reasons provided by Seema are correct. Therefore, water is indeed classified as a compound, not an element.

### Answer
The correct reasons are: **I, II, and III.**

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