Volume by Volume Percentage:

The volume by volume percentage is a way to express the concentration of a solute in a solution. It represents the volume of the solute (in this case, acetic acid) per 100 volumes of the solution (in this case, water).

To calculate the volume by volume percentage, we need to determine the volume of the solute (acetic acid) and the volume of the solution (acetic acid + water).

Given Data:
- Volume of acetic acid = 200 ml
- Volume of water = 400 ml

Step 1: Calculate the total volume of the solution:
The total volume of the solution is the sum of the volume of the solute (acetic acid) and the volume of the solvent (water).

Total volume of the solution = Volume of acetic acid + Volume of water
Total volume of the solution = 200 ml + 400 ml = 600 ml

Step 2: Calculate the volume by volume percentage:
The volume by volume percentage can be calculated using the formula:

Volume by volume percentage = (Volume of solute / Total volume of solution) x 100

Substituting the given values into the formula:

Volume by volume percentage = (200 ml / 600 ml) x 100
Volume by volume percentage = 33.33%

Conclusion:
The volume by volume percentage of the acetic acid solution is 33.33%. This means that for every 100 volumes of the solution, 33.33 volumes are acetic acid.