Question

If the mole fraction of urea in aqueous solution is 0.1 then the mass percentage of urea in the solution will be​

Answer 1

Molar mass of urea = 60 gm/mol

Molar mass of water =18 gm/mol

Mole fraction of solute = Moles of solute/( Solute moles + Solvent moles)

0.1 = moles of solute/moles of solute + moles of solvent

Let the solute moles + solvent moles be = 1

= 0.1=moles of solute(urea) = 0.6 gm

= 0.9 = moles of solvent(water) = 16.2 gm

Total mass of solution = 0.6 +16.2 = 16.8 gm

Volume= Mass/ Density

= 16.8/1000d  

Molarity = Moles of urea / l

Molarity = 0.1 / 16.8/1000d

Molarity = 1/10 x 1000/ 16.8

Molarity = 100/16.8 = 125/21

Molarity= 125 x 0.21/21

= 1.25 M

Thus the molarity of Urea in the solution is 1.25 M.