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Calculate the mass of urea (NH_2CONH_2)required in making 2.5 kg of 0.25 molal aqueous solution. |
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Answer» Solution :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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