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 14.14 grams of the compound were dissolved in 295.7 grams of diethyl ether, the solution began to boil at 34.835 °C. The compound was also found to be nonvolatile and a non-electrolyte. What is the molecular weight they determined for this compound ? ANSWER g/mol

Answer 1

Ans :

elevation in boiling point = boiling point of solution - boiling point of solvent

= 34.835 C - 34.500 C

= 0.335 C

Now molecular weight of the compound is given as :

M2 = ( w2 x Kb x 1000) / ( w1 x )

where M2 is molecular weight of compound

w2 is mass of compound added

kb = boiling point constant of solvent

w1 is mass of solvent

is boiling point elevation

putting all the values :

M2 = (14.14 x 2.02 x 1000) / (295.7 x 0.335)

= 288.3 g/mol

So the molecular weight of the compound is 288.3 g/mol