a chemist is studying small organic compounds for their potential use as an anti

Question

a chemist is studying small organic compounds for their potential use as an antifreez when 0.243 g of a compound is dissolved in 25ml of water the freezing point of the solution is -0.201C

A) calculate the molar mass of the compound (d of water =1.00g/ml)

B) analysis shows that the compound is 53.31 mass percent C and 11.18 mass percent H the reminder being O calculate the empirecle and molecular formulas of the compound

C)draw a lewis structure for a compound whit this formula that forms H bonds and another for one that does not.

Explanation / Answer

Calculate concentration of solution
0.243g in 25g H2O = 0.243/25*1000 = 9.72g in 1000g H2O
Kf for water = 1.86°C/m
The depression of the solution was 0.210°C

del Tf = i* kf* m [i=1]
Therefore molar mass = 1.86/0.210*9.72 = 86.091g/mol

Compound is
C = 53.31%
H = 11.18%
O = 35.51%
Divide by molar mass

C = 53.31/12.011 = 4.43843
H = 11.18 / 1.008 = 11.09127
O = 35.51 / 15.999 = 2.2195

Divide by 2.2195
C = 2.0 , H = 5.0, O = 1.0
Empirical formula = C2H5O
Molar mass C2H5O = (12.011*2) + (1.008*5) + 15.999 = 45.061

Calculated molar mass = 86.091

Nearest molecular formula = (C2H5O)*2 = C4H10O2

C) Expected structure = 2-Methyl-1,3-propanediol

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