Q4 of 53 Page 37

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

Given,


2.5 kg of 0.25 molal aqueous solution.


Molar mass of urea (NH2CONH2) = (2 (1 × 14 + 2 × 1) + 1 × 12 + 1 × 16)


= 60 g/mol


1000 g of water contains 0.25 mol = (0.25 × 60) g of urea.


= 15 g of urea.


Means, 1015 g of solution contains 15 g of urea


Therefore,


2500 g of solution contains =


= 36.95 g


Hence, mass of urea required is 37 g (approx).


More from this chapter

All 53 →
2

Calculate the mole fraction of benzene in solution containing 30% by mass in carbon tetrachloride.

 3

Calculate the molarity of each of the following solutions: (a) 30 g of Co(NO3)2. 6H2O in 4.3 L of solution (b) 30 mL of 0.5 M H2SO4 diluted to500 mL.

 4

Calculate (a) molality (b) molarity and (c) mole fraction of KI if the density of 20% (mass/mass) aqueous KI is 1.202 g mL-1.

 6

H2S, a toxic gas with rotten egg like smell, is used for the qualitative analysis. If the solubility of H2S in water at STP is 0.195 m, calculate Henry’s law constant.