The boiling point of diethyl ether , CH 3 CH 2 OCH 2 CH 3 , is 34.500 °C at 1 at

Question

The boiling point of diethyl ether, CH3CH2OCH2CH3, is 34.500 °C at 1 atmosphere. Kb(diethyl ether) = 2.02 °C/m

In a laboratory experiment, students synthesized a new compound and found that when 12.40 grams of the compound were dissolved in 236.2 grams of diethyl ether, the solution began to boil at 34.799 °C. The compound was also found to be nonvolatile and a non-electrolyte.


What is the molecular weight they determined for this compound ?

g/mol

The freezing point of water, H2O, is 0.000 °C at 1 atmosphere. Kf(water) = -1.86 °C/m

In a laboratory experiment, students synthesized a new compound and found that when 11.40 grams of the compound were dissolved in 263.1 grams of water, the solution began to freeze at -1.298 °C. The compound was also found to be nonvolatile and a non-electrolyte.

What is the molecular weight they determined for this compound ?

g/mol

Explanation / Answer

Boiling point elevation of diethyl ether = 34.799 - 34.500 = 0.299 C

Mass of solute = 12.4 g

mass of solvent = 236.2 g

Kb for diethyl ether = 2.022 C/m

Molality of solute = boiling point elevation / Kb

   = 0.299 C/ 2.022 C/m = 0.148 m

Molality = (mass of solute/ molar mass) * (1000/ mass of solvent)

0.148 m = (12.4 g / molar mass) * (1000 / 236.2 g)

So molar mass = 354.7 g/mol

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