Calculate the mass of urea (NH2CONH2) required in making 2.5 kg of 0.25 molal aqueous solution. Read more on Sarthaks.com - https://www.sarthaks.com/15237/calculate-the-mass-of-urea-nh2conh2-required-in-making-2-5-kg

Question

Calculate the mass of urea (NH2CONH2) required in making 2.5 kg of 0.25 molal aqueous solution.

Answer 1

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 (NH₂CONH₂) = 60 g mol
1. 0.25moleofurea=0.25mol×60gmol1=15g 
Total mass of solution=1000+15g=1015g=1.015kg

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

\(\frac{15g}{1.015kg}\times2.5kg=37g\)