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calculate molar mass using freezing points?
I am not asking for simply an answer because that will not help me. I would like help UNDERSTANDING this problem rather than just getting an answer. I don't understand how to calculate it when a freezing point is involved.
A solution of 5.00 g of lauryl alcohol in 0.100kg of benzene freezes at 4.1 Celsius. What is the molar mass of lauryl alcohol? Benzene has a normal freezing point of 5.5 Celsius and a Kf value of 5.12 Celsius/m.
2 Answers
- PupuLv 47 years agoFavorite Answer
∆T = Kf * m
m = number of moles of lauryl alcohol per kilogram of benzene.
Number of moles = (5/(molar mass)
m = (5/(molar mass) ÷ 0.1 = 50/(molar mass)
∆T = 5.5 – 4.1 = 1.4
1.4 = 5.12 * 50/(molar mass)
Molar mass = 256/1.4
This is approximately 182.9 g
Source(s): Google Tutor Teddy for more answers - electron1Lv 77 years ago
The Kf value tells you the number of degrees that the freezing point decreases for 1mole of the solute in 1 kilogram of the solvent. Use the following equation.
âT = Kf * m
m represents the number of moles of lauryl alcohol per kilogram of benzene.
Number of moles = (5/(molar mass)
m = (5/(molar mass) ÷ 0.1 = 50/(molar mass)
âT = 5.5 – 4.1 = 1.4
1.4 = 5.12 * 50/(molar mass)
Molar mass = 256/1.4
This is approximately 182.9 g
The formula for lauryl alcohol is below.
C12H26O
The molar mass is 186 g
