What is the freezing point of a 50% by volume ethanol solution? Assume water is the solvent. (Use data from Table 12.7 in textbook -for your reference, the text is ‘Chemistry a Molecular Approach’ by Tro et al).

1 Answer
Feb 22, 2018

Recall,

#DeltaT_f = iK_fm#

#50%# by volume ethanol solution is equal to (assuming #100"mL"#),

#50"mL" * (1.0"g")/("mL") * "kg"/(10^3"g") approx 5.0*10^-2"kg"# of water, and,

#50"mL" * (0.789"g")/("mL") * "mol"/(46.07"g") approx 0.856"mol"# of ethanol.

Hence,

#DeltaT_f = 1 * (1.86°C)/m * (0.856"mol")/(5.0*10^-2"kg")#

#therefore T_f = 31.9°C#,

and by extension #-31.9°C# is the freezing point of that particular solution.

Note, I don't have your text, so I used data from literature. If you see something in my work that is inconsistent with your text, just re-run the calculations.