To 5.85 gm of NaCl one kg of water is added to prepare a solution. What is the strength of NaCl in this solution (mol. wt. Of NaCl = 58.5)

Options

A. 0.1 Normal
B. 0.1 Molal
C. 0.1 Molar
D. 0.1 Formal

Explanation

To find the strength of NaCl in the solution, we need to determine the number of moles of NaCl and then calculate the strength in terms of molality (moles of solute per kilogram of solvent).

### Step 1: Calculate the number of moles of NaCl
To find the number of moles of NaCl, we use the formula:

\[ \text{Number of moles} = \frac{\text{mass of solute (g)}}{\text{molar mass of solute (g/mol)}} \]

Given:
- Mass of NaCl = 5.85 g
- Molar mass of NaCl = 58.5 g/mol

Substituting the values:

\[ \text{Number of moles of NaCl} = \frac{5.85 \, \text{g}}{58.5 \, \text{g/mol}} = 0.1 \, \text{mol} \]

### Step 2: Calculate the mass of the solvent
The mass of the solvent (water) is given as 1 kg.

### Step 3: Calculate the molality of the solution
Molality (m) is defined as the number of moles of solute per kilogram of solvent. The formula for molality is:

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

Substituting the values:

\[ \text{Molality} = \frac{0.1 \, \text{mol}}{1 \, \text{kg}} = 0.1 \, \text{mol/kg} \]

### Final Answer
The strength of NaCl in the solution is **0.1 mol/kg**.

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