The molarity of a solution of sodium chloride (mole wt. = 50.5) in water containg 5.85 gm of sodium chloride in 500 ml of solution is

Options

A. `0.25`
B. `2.0`
C. `1.0`
D. `0.2`

Answer

To find the molarity of a sodium chloride (NaCl) solution, we can follow these steps:

### Step 1: Calculate the number of moles of sodium chloride (NaCl).
To calculate the number of moles, 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:

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

### Step 2: Convert the volume of the solution from milliliters to liters.
Since molarity is expressed in moles per liter, we need to convert the volume from milliliters to liters.

Given:
- Volume of solution = 500 mL

To convert to liters:

\[ \text{Volume in liters} = \frac{500 \, \text{mL}}{1000} = 0.5 \, \text{L} \]

### Step 3: Calculate the molarity of the solution.
Molarity (M) is defined as the number of moles of solute per liter of solution:

\[ \text{Molarity (M)} = \frac{\text{Number of moles of solute}}{\text{Volume of solution in liters}} \]

Substituting the values we found:

\[ \text{Molarity (M)} = \frac{0.1 \, \text{moles}}{0.5 \, \text{L}} = 0.2 \, \text{M} \]

### Conclusion
The molarity of the sodium chloride solution is **0.2 M**.

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