If you have 200.0 mL of a 30.0% aqueous solution of isopropyl alcohol, what volume of water is in the solution?
Who knows? 30% in 200 mL solution means 60 g isopropyl alcohol with enough water added to make a total volume of 200 mL of solution. That will be 200-60 = 140 mL water IF (and ONLY IF) the volumes of isopropyl alcohol and water are additive. I expect they are not. For example, 500 mL ethyl alcohol added to 500 mL water gives a total volume very close to 950 mL (not 1000 which makes it about 50 mL short).
To find the volume of water in the solution, we need to subtract the volume of isopropyl alcohol from the total volume of the solution.
First, let's calculate the volume of isopropyl alcohol in the solution:
Volume of isopropyl alcohol = (percentage concentration / 100) * total volume of the solution
Given:
Percentage concentration of isopropyl alcohol = 30.0%
Total volume of the solution = 200.0 mL
Plug in the values:
Volume of isopropyl alcohol = (30.0 / 100) * 200.0 mL
Volume of isopropyl alcohol = 60.0 mL
Now, to find the volume of water:
Volume of water = Total volume of the solution - Volume of isopropyl alcohol
Volume of water = 200.0 mL - 60.0 mL
Volume of water = 140.0 mL
Therefore, there is 140.0 mL of water in the solution.