Question

5×10-3 kg of urea is dissolved in 2×10-2 kg of H2O calculate mass percent of unit​

Answer 1

Answer:

here's your answer

Explanation:

Given: Mass of solute, Urea=W

2

=1.0×10−3kg=1g

Mass of solvent=W

2

=0.0985kg=98.5g

∴ ΔT=0.211k

Molar mass of urea (NH

2

CONH

2

)=M

2

=60g/mol.

Mass of unknown substance=W

2

=1.6×10

−3

kg=1.6g

Mass of a Solvent=W

1

′

=0.086kg

∴ΔT

F

=0.34k

Molar mass of unknown substance=M

2

′

=?

This problem will be done in two parts

(i) To calculate molal depression constant

′

k

f

′

,

For urea solution-

ΔT

F

=K

f

×

W

1

×M

2

W

2

×1000

∴K

f

=

W

2

×1000

ΔT

F

×W

1

×M

2

=

1×1000

0.211×98.5×60

=

1000

1247.01

=1.24701

∴K

F

=1.2g/mol.

(ii) To calculate molar mass, M

2

For unknown solution

M

2

′

=K

F

×

W

1

′

×0.34

W

2

′

×1000

∴K

F

=

86×0.34

1.2×1.6×1000

=

29.24

1920

∴M

2

′

=65.66g/mol.

Hence, the molar mass of another solution is 65.66g/mol

Answer 2

Answer:

20% percentage of urea

Explanation:

molecular weight is 60 gram / mol