To a 4L of 0.2M solution of `NaOH, 2L` of `0.5M NaOH` are added. The molarity of resulting solution is

Options

A. 0.9M
B. 0.3M
C. 1.8M
D. 0.18M

Explanation

To find the molarity of the resulting solution when mixing two solutions of NaOH, we can follow these steps:

### Step 1: Calculate the number of moles of NaOH in each solution.

1. **For the first solution (4L of 0.2M NaOH):**
\[ \text{Moles of NaOH} = \text{Volume (L)} \times \text{Molarity (M)} = 4 \, \text{L} \times 0.2 \, \text{mol/L} = 0.8 \, \text{mol} \]

2. **For the second solution (2L of 0.5M NaOH):**
\[ \text{Moles of NaOH} = \text{Volume (L)} \times \text{Molarity (M)} = 2 \, \text{L} \times 0.5 \, \text{mol/L} = 1.0 \, \text{mol} \]

### Step 2: Calculate the total number of moles of NaOH in the mixture.

\[ \text{Total moles of NaOH} = \text{Moles from first solution} + \text{Moles from second solution} = 0.8 \, \text{mol} + 1.0 \, \text{mol} = 1.8 \, \text{mol} \]

### Step 3: Calculate the total volume of the resulting solution.

\[ \text{Total Volume} = \text{Volume of first solution} + \text{Volume of second solution} = 4 \, \text{L} + 2 \, \text{L} = 6 \, \text{L} \]

### Step 4: Calculate the molarity of the resulting solution.

\[ \text{Molarity (M)} = \frac{\text{Total moles of solute}}{\text{Total volume of solution (L)}} = \frac{1.8 \, \text{mol}}{6 \, \text{L}} = 0.3 \, \text{M} \]

### Final Answer:
The molarity of the resulting solution is **0.3 M**.

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