The mass of NaCl required to prepare 0.02 m aqueous solution in 1kg water is

Explanation

To find the mass of NaCl required to prepare a 0.02 molal aqueous solution in 1 kg of water, we can follow these steps:

### Step 1: Understand the definition of molality
Molality (m) is defined as the number of moles of solute per kilogram of solvent. The formula is given by:

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

### Step 2: Identify the given values
From the problem, we know:
- Molality (m) = 0.02 mol/kg
- Mass of solvent (water) = 1 kg

### Step 3: Rearrange the molality formula to find the number of moles of solute
We can rearrange the formula for molality to find the number of moles of NaCl:

\[ \text{Number of moles of NaCl} = m \times \text{Mass of solvent in kg} \]

Substituting the known values:

\[ \text{Number of moles of NaCl} = 0.02 \, \text{mol/kg} \times 1 \, \text{kg} = 0.02 \, \text{mol} \]

### Step 4: Calculate the mass of NaCl using its molar mass
The molar mass of NaCl is approximately 58.5 g/mol. We can find the mass of NaCl using the formula:

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

Substituting the values we have:

\[ \text{Mass of NaCl} = 0.02 \, \text{mol} \times 58.5 \, \text{g/mol} = 1.17 \, \text{g} \]

### Conclusion
The mass of NaCl required to prepare a 0.02 molal aqueous solution in 1 kg of water is **1.17 grams**.

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