The mass of NaCl required to prepare 0.04 m aqueous solution in 1kg water is

Explanation

To find the mass of NaCl required to prepare a 0.04 molal (m) aqueous solution in 1 kg of water, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Molality**:
Molality (m) is defined as the number of moles of solute (in this case, NaCl) per kilogram of solvent (water).

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

2. **Identify Given Values**:
- Molality (m) = 0.04 m
- Mass of solvent (water) = 1 kg

3. **Use the Formula for Molality**:
Rearranging the formula for molality gives us the number of moles of solute:

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

Substituting the known values:

\[ \text{Number of moles of NaCl} = 0.04 \, \text{m} \times 1 \, \text{kg} = 0.04 \, \text{moles} \]

4. **Calculate the Mass of NaCl**:
To find the mass of NaCl, we need to use its molar mass. The molar mass of NaCl is approximately 58.5 g/mol.

Using the formula:

\[ \text{Mass of NaCl} = \text{Number of moles} \times \text{Molar mass} \]

Substituting the values:

\[ \text{Mass of NaCl} = 0.04 \, \text{moles} \times 58.5 \, \text{g/mol} = 2.34 \, \text{grams} \]

5. **Final Answer**:
The mass of NaCl required to prepare a 0.04 m aqueous solution in 1 kg of water is **2.34 grams**.