Question #c25e3

2 Answers
Oct 10, 2015

400-86/400 *100

Oct 10, 2015

Answer:

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.