Question

Calculate the mass of urea in 100g of H2O in 0.3 molal solution.

Answer 1

Answer:

0.25 molal aqueous solution of urea means that 0.25 mole of urea are present in 1 kg of water  

Moles of urea = 0.25mole  

Mass of solvent (water) = 1 kg = 1000 g  

Molar mass of urea (NH  

2

​  

CONH  

2

​  

) = 60 g mol

1. 0.25moleofurea=0.25mol×60gmol1=15g  

Totalmassofsolution=1000+15g=1015g=1.015kg

Thus; 1.015 kg of solution contain urea = 15g×2.5kg of solution will require urea

1.015kg

15g

​  

×2.5kg = 37 g  

HIH:)