The mass of NaCl required to prepare 0.05 m aqueous solution in 1kg water is

Answer

To find the mass of NaCl required to prepare a 0.05 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 for molality is:
\[ m = \frac{\text{Number of moles of solute}}{\text{Mass of solvent in kg}} \]

### Step 2: Identify the given values
From the question, we have:
- Molality (m) = 0.05 mol/kg
- Mass of solvent (water) = 1 kg

### Step 3: Calculate the number of moles of NaCl needed
Using the formula for molality, we can rearrange it 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:
\[ \text{Number of moles of NaCl} = 0.05 \, \text{mol/kg} \times 1 \, \text{kg} = 0.05 \, \text{mol} \]

### Step 4: Calculate the mass of NaCl
To find the mass of NaCl, we use the formula:
\[ \text{Mass of NaCl} = \text{Number of moles} \times \text{Molar mass of NaCl} \]
The molar mass of NaCl is approximately 58.5 g/mol. Therefore:
\[ \text{Mass of NaCl} = 0.05 \, \text{mol} \times 58.5 \, \text{g/mol} = 2.925 \, \text{g} \]
Rounding this to two decimal places, we get:
\[ \text{Mass of NaCl} \approx 2.93 \, \text{g} \]

### Final Answer
The mass of NaCl required to prepare a 0.05 molal aqueous solution in 1 kg of water is approximately **2.93 grams**.

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