500 ml. aq. Solution of ethanol `(C_(2)H_(5)OH)` contains 20 ml of
ethanol. Find v/v%

Answer

To find the volume/volume percentage (v/v%) of ethanol in the aqueous solution, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the given values:**
- Volume of ethanol (solute) = 20 ml
- Total volume of the solution = 500 ml

2. **Use the formula for volume percent (v/v%):**
\[ \text{v/v\%} = \left( \frac{\text{Volume of solute}}{\text{Volume of solution}} \right) \times 100 \]

3. **Substitute the known values into the formula:**
\[ \text{v/v\%} = \left( \frac{20 \, \text{ml}}{500 \, \text{ml}} \right) \times 100 \]

4. **Calculate the fraction:**
\[ \frac{20}{500} = 0.04 \]

5. **Multiply by 100 to find the percentage:**
\[ 0.04 \times 100 = 4\% \]

6. **Conclusion:**
The volume/volume percentage (v/v%) of ethanol in the solution is **4%**.