Answer to Question #269975 in Organic Chemistry for matt

Question

Find the mole fraction of 18.93% m/m of ethylene glycol in 112 g of aqueous ethylene glycol solution.

Answer 1

As given in the question, a solution of ethylene glycol and water contains 20% of ethylene glycol by mass.

That is, in 112g of solution - 21.202g of ethylene glycol.

Molar mass of ethylene glycol - (12*2 + 1*6 + 16*2) = 62g/mol.

so, in 21.202g we have 21.202/62 = 0.342 mol.

remaining 90.8g contains water. Number of moles of water = 90.8/18 = 5.044 mol

Mole fraction of ethylene glycol = No of moles of ethylene glocal/ Total number of moles.

= 0.342/(0.342 + 5.044)

= 0.0635.

Mole fraction of water = 1-0.0635 = 0.9365