Question

calculate the mass of urea required in making of 2.5kg of 0.25 moral aqueous solution

Answer 1

=2.5/0.25
=2.5×100/0.25×100
250/25
10
therefore 10 kg mass of urea will be required.

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Answer 2

Hey !!

Mass of required aqueous solution = 2.5 kg = 2500 g

0.25 molal aqueous solution of urea it means that 0.25 mole of urea is dissolved in 1000 grams of water.

Mass of water = 1000 g

Mass of urea = 0.25 mol

Molar mass of urea (H₂NCONH₂) = 4 × 1 + 2 × 14 + 1 × 12 + 1 × 16 = 60 g mol⁻¹

        NOTE :- Mass of urea = Number of moles of urea × Molar mass of urea  

     Mass of 0.25 moles of urea = 0.25 mol ×× 60 h mol⁻¹ = 15 g

Mass of solution = 1000 g + 15 g = 1015 g

1015 g of aqueous solution contains urea = 15 g

∴ 2500 g of aqueous solution will require urea  

         = 15 g / 1015 kg × 2500 g  

            = 36.95 g

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