Answer:
You should add water to the 10 ml ethanol until you have a 100-ml solution. For this, pour the 10 ml ethanol in a 100-ml volumetric flask and add water until the mark that indicates that you have a volume of 100 ml. Don´t forget to mix before you reach the mark.
Explanation:
You can assume that your ethanol has a concentration of 1X.
if you have to dilute it ten times, the final concentration will be 1X / 10 = 0.1X
The number of moles of ethanol present in the solution will remain the same after the dilution because you are not adding nor substracting ethanol, that means:
mol ethanol before dilution = mol ethanol after dilution
The number of moles can be expressed in this form:
mol ethanol = volume of the solution * concentration of ethanol
then, to find how much water you have to add you have to solve the final volume (Vf) from this equation:
mol ethanol before dilution = mol ethanol after dilution
Vi * Ci = Vf * Cf
where:
Vi = volume of the solution before dilution.
Ci = concentration of the solution before dilution
Vf = volume of the final solution
Cf = concentration of the final solution
Replacing with the data:
10 ml * 1X = Vf * 0.1X
10 ml *1X / 0.1X = Vf
100 ml = Vf
