Question

Calculate the mole fraction of urea in a solution containing 12g of urea in 80 g of H2O (Molar mass of urea = 60 g/mole

Answer 1

Given data :-

→ weight of urea = 12 g

→ weight of water (H2O ) = 80 g

{Molar mass of urea = 60 g/mole }

Solution :-

Here, solute is urea and solvent is water

Now,

→ Number of moles of a urea

= mass of urea/molar mass of the urea

→ Number of moles of a urea = 12/60

→ Number of moles of a urea = 1/5

→ Number of moles of a urea = 0.2 mol of urea

→ Number of moles of a water

= mass of water/molar mass of the water

→ Number of moles of a water = 80/18

→ Number of moles of a water = 40/9

→ Number of moles of a water = 4.44 mol of water

Here we need to find :

→ Total moles in solution

= Number of moles of a urea + Number of moles of a water

→ Total moles in solution = 0.2 + 4.44

→ Total moles in solution = 4.64

Now

→ Mole fraction of urea

= moles of urea/total moles in solution

→ Mole fraction of urea = 0.2/4.64

→ Mole fraction of urea = 5/116

→ Mole fraction of urea = 0.0431

Hence, mole fraction of urea is 0.0431

{ Note :- Mole fraction denoted by ' x ' and mole fraction is independent of temperature and it has no unit }