Solutions

Given, Mass of solute

%5Cleft(w_%7BB%7D%5Cright)%3D10%20%5C%2Cg

Molar mass of solute

%5Cleft(M_%7BB%7D%5Cright)%3DM_%7BB%7D

Mass of solvent

%5Cleft(w_%7BA%7D%5Cright)%3D360%20%5C%2Cg

Relative lowering in vapour pressure of solution

%3D5%20%5Ctimes%2010%5E%7B-3%7D

Molar mass of water

%5Cleft(M_%7BA%7D%5Cright)%3D18%20%5C%2Cg%20%5C%2Cmol%20%5E%7B-1%7D

%5Cbecause%20%5Cfrac%7B%5CDelta%20p%7D%7Bp%5E%7B%5Ccirc%7D%7D%3D

Relative lower in vapour-pressure of solution.

%5Cfrac%7B%5CDelta%20p%7D%7Bp%5E%7B%5Ccirc%7D%7D%3D%5Cchi_%7BB%7D

%5CRightarrow%20%5Cfrac%7Bn_%7BB%7D%7D%7Bn_%7BA%7D%2Bn_%7BB%7D%7D%3D5%20%5Ctimes%2010%5E%7B-3%7D

where,

n_%7BA%7D

and

n_%7BB%7D

are number of moles of solvent (A) and solute

(B)

respectively.

n_%7BA%7D%3D%5Cfrac%7B360%7D%7B18%7D%3D20

n_%7BB%7D%3D%5Cfrac%7Bw_%7BB%7D%7D%7BM_%7BB%7D%7D%3D%5Cfrac%7B10%7D%7BM_%7BB%7D%7D

%5Cbecause%205%20%5Ctimes%2010%5E%7B-3%7D%3D%5Cchi_%7BB%7D%3D%5Cfrac%7B%5Cfrac%7B10%7D%7BM_%7BB%7D%7D%7D%7B20%2B%5Cfrac%7B10%7D%7BM_%7BB%7D%7D%7D

5%20%5Ctimes%2010%5E%7B-3%7D%3D%5Cfrac%7B%5Cfrac%7B10%7D%7BM_%7BB%7D%7D%7D%7B%5Cfrac%7B20%20M_%7BB%7D%2B10%7D%7BM_%7BB%7D%7D%7D

5%20%5Ctimes%2010%5E%7B-3%7D%3D%5Cfrac%7B10%7D%7B20%5C%2C%20M_%7BB%7D%2B10%7D

%5Cleft(20%5C%2C%20M_%7BB%7D%2B10%5Cright)%205%20%5Ctimes%2010%5E%7B-3%7D%20%3D10

or,

20%5C%2C%20M_%7BB%7D%2B10%20%3D%5Cfrac%7B10%7D%7B5%7D%20%5Ctimes%2010%5E%7B3%7D

20%20M_%7BB%7D%2B10%20%3D2000

%5CRightarrow%2020%20%5C%2CM_%7BB%7D%3D1990

M_%7BB%7D%20%3D%5Cfrac%7B1990%7D%7B20%7D%3D99.5%20%5C%2Cg%20%5C%2Cmol%20%5E%7B-1%7D

Chapter Questions
1 MCQs