Assertion :- One molal aqueous solution of urea contains 60g of urea in 1kg (1000 g) water.
Reason :- Solution containing one mole of solute in 1000g solvent is called as one molal solution.

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are true but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If the assertion and reason both are false.

Explanation

To determine the validity of the assertion and reason provided in the question, we will analyze both statements step by step.

### Step 1: Understanding the Assertion
The assertion states that "One molal aqueous solution of urea contains 60g of urea in 1kg (1000 g) water."

- A molal solution is defined as a solution that contains one mole of solute per kilogram of solvent.
- Urea (chemical formula: CO(NH2)2) has a molar mass of approximately 60 g/mol.

**Calculation:**
- To find out how many grams of urea are in one mole, we use its molar mass:
- 1 mole of urea = 60 g of urea.

Thus, in a 1 molal solution, we would indeed have 60 g of urea dissolved in 1 kg of water.

### Step 2: Understanding the Reason
The reason states that "A solution containing one mole of solute in 1000g solvent is called a one molal solution."

- This definition aligns perfectly with the definition of molality.
- Molality (m) is defined as:
\[ m = \frac{\text{moles of solute}}{\text{mass of solvent in kg}} \]
- Therefore, having one mole of solute in 1000 g (or 1 kg) of solvent is indeed the definition of a 1 molal solution.

### Conclusion
Both the assertion and the reason are correct. A one molal aqueous solution of urea does contain 60 g of urea in 1 kg of water, and the definition of a molal solution is accurately stated.

### Final Answer
- **Assertion:** True
- **Reason:** True
- **Conclusion:** Both the assertion and the reason are correct.

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