Question

8.0575 x 10-2 kg of Glauber's salt are dissolved
in water to obtain 1 dm? of a solution of density
1077.2 kg m-3. Calculate the molarity, molality, and
mole fraction of Na2SO4 in the solution.​

Answer 1

Answer:

The formula for Glauber's salt is Na

2

SO

4

⋅10H

2

O.

Given mass =8.0575×10

−2

kg=80.575kg

Molecular weight =322gmol

−1

Molecular weight of Na

2

SO

4

=142gmol

−1

Mass of Na

2

SO

4

in 80.575 g sampe =

322

142

×80.575 =35.53g

Molarity (M) =

142

35.52

×1=0.2502M

Density=1077.2kgm

−3

=1077.2gL

−1

Density=

Volume

Mass

Mass of solution =density×volume =1077.2×1=1077.2g

Mass of water =1077.2−35.53=1041.67g

Molality(m)=

142

35.53

×

1041.67

1

×100=0.2402

Moles of Na

2

SO

4

=

142

35.53

=0.2502

Moles of H

2

O=

18

1041.67

=57.87

Moles fraction (Na

2

SO

4

)=

Total Moles

Moles ofNa

2

SO

4

=

0.2502+57.87

0.2502

=4.304×10

−3