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%
