Molarity of 4% (w/v) solution of NaOH is

Options

A. `0.1`
B. `0.5`
C. `0.001`
D. `1.0`

Explanation

To find the molarity of a 4% (w/v) solution of NaOH, we can follow these steps:

### Step 1: Understand the Definition of % (w/v)
A 4% (w/v) solution means that there are 4 grams of solute (NaOH) in every 100 mL of solution.

### Step 2: Calculate the Number of Moles of NaOH
To find the number of moles of NaOH, we use the formula:
\[ \text{Number of moles} = \frac{\text{Weight of NaOH (g)}}{\text{Molecular weight of NaOH (g/mol)}} \]
The molecular weight of NaOH can be calculated as follows:
- Atomic mass of Na = 23 g/mol
- Atomic mass of O = 16 g/mol
- Atomic mass of H = 1 g/mol

So, the molecular weight of NaOH = 23 + 16 + 1 = 40 g/mol.

Now, substituting the values:
\[ \text{Number of moles} = \frac{4 \text{ g}}{40 \text{ g/mol}} = 0.1 \text{ moles} \]

### Step 3: Convert the Volume of Solution to Liters
The volume of the solution is given as 100 mL. To convert this to liters:
\[ \text{Volume in liters} = \frac{100 \text{ mL}}{1000} = 0.1 \text{ L} \]

### Step 4: Calculate the Molarity
Molarity (M) is defined as the number of moles of solute per liter of solution:
\[ \text{Molarity (M)} = \frac{\text{Number of moles of solute}}{\text{Volume of solution in liters}} = \frac{0.1 \text{ moles}}{0.1 \text{ L}} = 1 \text{ M} \]

### Final Answer
The molarity of the 4% (w/v) solution of NaOH is **1 M**.

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