4gm of NaOH is dissolved in 250ml of a solution. calculate its molarity.

Explanation

To calculate the molarity of a solution where 4 grams of NaOH is dissolved in 250 mL, follow these steps:

### Step 1: Understand the formula for molarity
Molarity (M) is defined as the number of moles of solute divided by the volume of the solution in liters.

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

### Step 2: Convert the volume from mL to liters
Given that the volume of the solution is 250 mL, we need to convert this to liters:

\[ \text{Volume in liters} = \frac{250 \text{ mL}}{1000} = 0.250 \text{ L} \]

### Step 3: Calculate the number of moles of NaOH
To find the number of moles, use the formula:

\[ \text{Number of moles} = \frac{\text{Given mass (g)}}{\text{Molecular weight (g/mol)}} \]

The molecular weight of NaOH (Sodium Hydroxide) is approximately 40 g/mol. Therefore:

\[ \text{Number of moles} = \frac{4 \text{ g}}{40 \text{ g/mol}} = 0.1 \text{ moles} \]

### Step 4: Substitute the values into the molarity formula
Now that we have the number of moles and the volume in liters, we can substitute these values into the molarity formula:

\[ \text{Molarity} = \frac{0.1 \text{ moles}}{0.250 \text{ L}} = 0.4 \text{ M} \]

### Conclusion
The molarity of the NaOH solution is 0.4 M.

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