Calculate the mass of urea (NH2CONH2) r...

Calculate the mass of urea `(NH_2CONH_2)` required in making 2.5 kg of 0.25 molal aqueous solution.

Text Solution

Verified by Experts

0.25 molal aqueous solution of urea means 0.25 moles of urea are present in 1000 g of water. Molar mass of urea `(NH_2 CONH_2) = 60 g "mol"^(-1)`
` therefore ` 0.25 mole of urea contains 0.25 mole `xx 60 g "mol"^(-1) = 15 g`
Total mass of solution = 1000 g + 15 g = 1015 g = 1.015 kg
Thus, 1.015 kg of solution contain urea = 15 g
2.5 kg of solution will require urea = `(15)/(1.015) xx 2.5 = 36.946 g `

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What is the mass of urea required for making 2.5 kg of 0.25 molal aqueous solution?

37 g

25 g

125 g

27.5 g

Calculate the mass of anhydrous Na_2CO_3 required to prepare 250 ml 0.25 M solution .

6.225 g

66.25 g

6.0 g

6.625 g

Mole fraction of a solute in 2.5 molal aqueous solution is

`0.43`

`0.043`

`4.3`

`43`