Question

60 g of urea is dissolved in 90 g of water. Then, the molefraction of solute is
a)1/5
b)1/6
c)5/6
d)4/5
I want with solution
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Answer 1

Answer:

$60kg = 6000gm \: of \: water \\ water \: 90gm \\ = moles \: of \: {h}^{2} o = \frac{90}{18} = 5 \\ moles \: of \: water \: = \frac{6000}{600} = 100 \\ moles \: fraction \: of \: water = \frac{5}{100 + 5} = \frac{5}{(10s + 31)} = \frac{1}{51}$

Answer 2

Given:-

→ Mass of urea = 60g

→ Mass of water = 90g

To find:-

→ Mole fraction of solute.

Solution:-

It is clear that urea is solute and water is solvent. So, we have to calculate the mole fraction of urea.

• Molar mass of Carbon (C) = 12 g/mol

• Molar mass of Hydrogen (H) = 1 g/mol

• Molar mass of Oxygen (O) = 16 g/mol

• Molar mass of Nitrogen (N) = 14 g/mol

Hence, molar mass of urea [CH₄N₂O] :-

= 12 + 1×4 + 14×2 + 16

= 12 + 4 + 28 + 16

= 60 g/mol

And, molar mass of water [H₂O] :-

= 1×2 + 16

= 18 g/mol

Number of moles in 60g of urea :-

= Given Mass/Molar mass

= 60/60

= 1 mole

Number of moles in 90g of water :-

= Given Mass/Molar mass

= 90/18

= 5 moles

Mole fraction of solute :-

= Mole of solute/Total mole in solution

= 1/(1 + 5)

= 1/6

Thus, mole fraction of solute [urea] is 1/6 [Option.b]