3g of a salt [mol. Wt. 30] is dissolved in 250 g of water the molality of the solution is

Options

A. `0.4`
B. `0.2`
C. `0.6`
D. `0.8`

Explanation

To calculate the molality of the solution, we can follow these steps:

### Step 1: Identify the given data
- Mass of the solute (salt) = 3 g
- Molecular weight of the solute = 30 g/mol
- Mass of the solvent (water) = 250 g

### Step 2: Convert the mass of the solvent from grams to kilograms
To use the molality formula, we need the mass of the solvent in kilograms:
\[ \text{Mass of solvent in kg} = \frac{250 \text{ g}}{1000} = 0.25 \text{ kg} \]

### Step 3: Calculate the number of moles of the solute
The number of moles of solute can be calculated using the formula:
\[ \text{Number of moles} = \frac{\text{mass of solute}}{\text{molecular weight of solute}} \]
Substituting the values:
\[ \text{Number of moles} = \frac{3 \text{ g}}{30 \text{ g/mol}} = 0.1 \text{ mol} \]

### Step 4: Calculate the molality of the solution
Molality (m) is defined as the number of moles of solute per kilogram of solvent:
\[ \text{Molality} = \frac{\text{Number of moles of solute}}{\text{Mass of solvent in kg}} \]
Substituting the values:
\[ \text{Molality} = \frac{0.1 \text{ mol}}{0.25 \text{ kg}} = 0.4 \text{ mol/kg} \]

### Final Answer
The molality of the solution is **0.4 mol/kg**.

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