Question

When a solution containing w g of urea in 1 kg of water is cooled to -372c ,200 g of ice is separated?

Answer 1

Answer:

29.7g

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Explanation:

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Answer 2

Given info : A solution containing w g of urea in 1kg of water is cooled to 272K,200g of ice is separated. k of water = 1.86 K kg/mol.

To find : The mass of urea, w , is ...

solution : mass of water = 1 kg = 1000g

mass of ice is separated = 200g

so mass of remaining water = 1000g - 200g = 800g

mass of urea = w g

molecular mass of urea = 60 g/mol

so no of moles of urea = (w/60)

molality = no of moles of urea/mass of water in kg

= (w/60)/(800/1000)

= w/48

now using formula, ∆Tf = k × m

⇒(273.15 - 272) = 1.86 × w/48

⇒1.15 × 48/1.86 = w

⇒w = 29.7 g

Therefore the mass of urea is 29.7 g