Question

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

Answer 1

_/\_Hello mate__here is your answer--

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Molar mass of urea (NH2CONH2)

= 2(1 × 14 + 2 × 1) + 1 × 12 + 1 × 16

= 60 g mol^−1

0.25 molar aqueous solution of urea means:

1000 g of water contains 0.25 mol

= (0.25 × 60)g of urea

= 15 g of urea

That is,

(1000 + 15) g of solution contains 15 g of urea

Therefore, 2.5 kg (2500 g) of solution contains

= (15× 2500)/( 1000+ 15 )

=36.95 g

= 37 g of urea (approximately)

Hence, mass of urea required = 37 g

I hope, this will help you.☺

Thank you______❤

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Answer 2

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Given,

A molal solution is a solution that contains 1 molecular weight of solute in a kilogram of solvent.

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 = 15×2500/1015

= 36.95 g

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

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