A: For a given solution (density `1 gm//ml`), molality is greater than molarity.
R: Molarity involves volume of solution while molality involves mass of solvent.

Options

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

Answer

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

### Step 1: Understand the Definitions
- **Molarity (M)** is defined as the number of moles of solute per liter of solution.

\[ \text{Molarity (M)} = \frac{\text{Number of moles of solute}}{\text{Volume of solution in liters}} \]

- **Molality (m)** is defined as the number of moles of solute per kilogram of solvent.

\[ \text{Molality (m)} = \frac{\text{Number of moles of solute}}{\text{Mass of solvent in kg}} \]

### Step 2: Analyze the Given Density
The density of the solution is given as 1 g/mL. This means:
- 1 mL of solution weighs 1 g.
- 1 kg of solution is equivalent to 1000 mL or 1 L of solution.

### Step 3: Compare Molarity and Molality
Since the density is 1 g/mL, we can infer:
- The mass of 1 L (1000 mL) of solution is 1000 g (or 1 kg).
- The mass of the solvent will always be less than the mass of the solution because the solution contains both solute and solvent.

If we denote the mass of the solute as \( m_s \) and the mass of the solvent as \( m_{solvent} \):
\[ m_{solution} = m_{solute} + m_{solvent} \]
Thus, \( m_{solvent} = 1000 g - m_s \).

### Step 4: Implications for Molarity and Molality
Given that molality is based on the mass of the solvent (which is less than the total mass of the solution), and molarity is based on the volume of the solution (which is 1 L in this case), we can conclude:
- Since the mass of the solvent is less than the mass of the solution, the denominator for molality (mass of solvent in kg) will be smaller than the denominator for molarity (volume of solution in L).
- Therefore, molality will be greater than molarity under these conditions.

### Step 5: Conclusion
- **Assertion (A)** is true: "For a given solution (density 1 g/mL), molality is greater than molarity."
- **Reason (R)** is also true: "Molarity involves volume of solution while molality involves mass of solvent."

Since both the assertion and reason are true, and the reason correctly explains the assertion, the correct answer is option 1.

### Final Answer:
**Option 1: Both assertion and reason are true, and reason is the correct explanation.**

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