Question

calculate the mass of urea (NH2CONH2) required in making 2.5 kilogram of 0.25 molal aqueous solution​

Answer 1

Answer:

Given that.

Mass of solution = 2.5 Kg.

Molality = 0.25 m.

Molar mass of urea (NH2CONH2) =14 + 2 × 1 + 12 + 16 + 14 + 2 × 1 = 60 g mol−1.

Let mass of urea (NH2CONH2) = w gram.

Number of moles of urea = w / 60 = 0.01667 mol.

Mass of urea in Kg = w/1000 = 0.001w kg.

Answer 2

Answer:

Given

Mass of solution = 2.5 Kg

Molality = 0.25 m

Molar mass of urea (NH2CONH2) =(14 + 2 × 1 + 12 + 16 + 14 + 2 × 1) = 60 g mol−1

Mass of urea = Number of moles of urea × Molar mass of urea

Mass of 0.25 moles of urea = 0.25 mol × 60 g 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 = 37 g

Mass of urea required required in making 25 grams of 0.25m = 37 grams

Hope it helps you....