Three grams of salt of molecular weight 30 is dissolved in `250 g` of water. The molality of the solution is….

Explanation

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

### Step 1: Understand the formula for molality
Molality (m) is defined as the number of moles of solute divided by the mass of solvent in kilograms.

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

### Step 2: Calculate the moles of solute
We know the mass of the solute (salt) and its molecular weight (molar mass). The formula to calculate moles is:

\[ \text{Moles of solute} = \frac{\text{Mass of solute (g)}}{\text{Molar mass (g/mol)}} \]

Given:
- Mass of solute = 3 g
- Molar mass = 30 g/mol

Now, substituting the values:

\[ \text{Moles of solute} = \frac{3 \text{ g}}{30 \text{ g/mol}} = 0.1 \text{ moles} \]

### Step 3: Convert the mass of solvent to kilograms
The mass of the solvent (water) is given as 250 g. To convert this to kilograms:

\[ \text{Mass of solvent (kg)} = \frac{250 \text{ g}}{1000} = 0.25 \text{ kg} \]

### Step 4: Substitute the values into the molality formula
Now we can substitute the moles of solute and the mass of solvent into the molality formula:

\[ \text{Molality (m)} = \frac{0.1 \text{ moles}}{0.25 \text{ kg}} = 0.4 \text{ mol/kg} \]

### Step 5: State the final answer
The molality of the solution is:

\[ \text{Molality} = 0.4 \text{ mol/kg} \]

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