13.
1.325 gm of 80% pure Na2Co3 is dissolved in 100 g of water - Molality of
the solution is.
(Ans :0.1m)
Answers
12th
Chemistry
Solutions
Expressing Concentration of Solutions
Define molality. How many g...
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Asked on October 15, 2019 by
Anita Yarramsetti
Define molality. How many grams of Na
2
CO
3
should be dissolved in 250 grams of water to prepare 0.1 m solution?
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VIDEO EXPLANATION
ANSWER
Molality is the number of moles of solute dissolved in 1 kg of solvent.
Molality=
mass of solvent in kg
number of moles of solute
Let W g of sodium carbonate are dissolved.
The molar mass of Na
2
CO
3
=2(23)+12+3(16)=46+12+48=106 g/mol
The number of moles of Na
2
CO
3
=
106 g/mol
W g
= 0.009434 W mol
Mass of water = 250 g= 0.250 kg
0.1 m=
0.250 kg
0.009434 W mol
W= 2.65 g
Hence, 2.65 grams of Na
2
CO
3
should be dissolved in 250 grams of water to prepare 0.1 m solution