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 11.20 grams of the compound were dissolved in 271.8 grams ofdiethyl ether, the solution began to boil at 34.593 °C. The compound was also found to be nonvolatile and a non-electrolyte.


What is the molecular weight they determined for this compound ?

Answer 1

Answer:

895.8g/mol

Explanation:

Hello, here the solution:

Consider the formula for the boiling-point elevation:

$T_{solution}-T_{solvent}=K_{boil}m_{solute}$

We solve for the molality of the solute:

$m_{solute}=\frac{T_{solution}-T_{solvent}}{ K_{boil}}=\frac{34.593C-34.5C}{2.02C/m}\\m_{solute}=0.046mol_{solute}/kg_{solvent}$

By knowing the mass of the diethyl ether (271.8 g =0.2718kg) and that 11.20g of the solute were dissolved, the molecular mass is given by:

$M_{solute}=\frac{11.20g_{solute}}{0.046\frac{mol_{solute}}{kg_{solvent}} *0.2718kg_{solvent}} \\M_{solute}=895.8g/mol$

Best regards.