Question #c25e3

2 Answers
Oct 10, 2015

400-86/400 *100

Oct 10, 2015

Your solution is 78.5% "v/v" ethanol.

Explanation:

A solution's percent concentration by volume is defined as the ratio between the volume of the solute, in your case ethanol, and the total volume of the solution, multiplied by 100.

"%v/v" = "volume of solute"/"volume of solution" xx 100

In your case, you know that the total volume of the solution is equal to "400 mL". Moreover, you know that this solution contains "86 mL" of water, which also implies that it must contain

V_"solution" = V_"water" + V_"ethanol"

V_"ethanol" = V_"solution" - V_"water"

V_"ethanol" = "400 mL" - "86 mL" = "314 mL ethanol"

The percent concentration by volume of ethanol in this solution is

"%v/v" = (314color(red)(cancel(color(black)("mL"))))/(400color(red)(cancel(color(black)("mL")))) xx 100 = color(green)("78.5%")

I'll leave the answer rounded to thre sig figs.