Question #7bb32

1 Answer
Jul 18, 2017

Answer:

#"26% v/v"#

Explanation:

The thing to keep in mind about a solution's volume by volume percent concentration, #"v/v %"#, is that is will always tell you the volume of solute present in #"100 mL"# of solution.

So in order to find a solution's volume by volume percent concentration, all you need to do is to figure out how many milliliters of solute are present for every #"100 mL"# of solution.

In this case, you know that the total volume of the solution is equal to

#overbrace("45 mL ethanol")^(color(blue)("volume of solute")) + overbrace("125 mL water")^(color(blue)("volume of solvent")) = overbrace("170 mL solution")^(color(blue)("volume of solution"))#

You know that this solution contains #"45 mL"# of solute in #"170 mL"# of solution, so you can say that #"100 mL"# of solution will contain

#100 color(red)(cancel(color(black)("mL solution"))) * "45 mL ethanol"/(170color(red)(cancel(color(black)("mL solution")))) = "26.47 mL ethanol"#

Therefore, you can say that this solution is

#color(darkgreen)(ul(color(black)("% v/v = 26% ethanol")))#

The answer must be rounded to two sig figs, the number of sig figs you have for your values.