Answer :

To determine how many milliliters of acetic acid are needed to make 500 mL of a 5.0% acetic acid solution (by volume/volume), follow these steps:

1. Understand the problem: We need to find the volume of acetic acid that will make up 5.0% of the total 500 mL solution.

2. Express the concentration as a decimal:
- A 5.0% concentration means that 5.0 mL of acetic acid is present in every 100 mL of solution.
- Converting this percentage to a decimal involves dividing by 100: [tex]\( 5.0\% = 5.0 / 100 = 0.05 \)[/tex].

3. Set up the relationship:
- The total volume of the solution is 500 mL.
- We need to find the volume of acetic acid that makes up 5.0% of this 500 mL solution.

4. Calculate the volume of acetic acid:
- Multiply the total volume of the solution by the decimal concentration:
[tex]\[ \text{Volume of acetic acid} = 500 \, \text{mL} \times 0.05 \][/tex]

5. Perform the multiplication:
- [tex]\( 500 \, \text{mL} \times 0.05 = 25 \, \text{mL} \)[/tex].

Therefore, 25 mL of acetic acid are needed to make 500 mL of a 5.0% acetic acid solution.