Question

Ethanol is used widely as a solvent in laboratories for various chemical reactions. A laboratory technician takes 50.0 mL of ethanol and dilutes it to 100.0 mL with distilled water. What is the percentage concentration by volume of the resulting solution?

Answer 1

This question is quite vague, as the initial concentration of ethanol is not provided. However, from experience I can tell you that most laboratory work is done with 98% ethanol, and not absolute ethanol (100%). So in order to calculate the final concentration, we need to take the given values, which includes the initial concentration (98%), the initial volume (50.0mL) and the final volume (100.0mL). We apply the following equation to calculate the final concentration:

C1V1 = C2V2
C1 = Initial concentration
C2 = Final concentration
V1 = Initial volume
V2 = Final volume

(98%)(50.0mL) = (C2)(100.0mL)
Therefore, the final concentration (C2) = 49%