Question

Vapour pressure of chloroform $$\left( {CHC{l_3}} \right)$$  and dichloromethane $$\left( {C{H_2}C{l_2}} \right)$$   at $${25^ \circ }C$$  are $$200\,mm\,Hg$$   and $$41.5\,mm\,Hg$$   respectively. Vapour pressure of the solution obtained by mixing $$25.5\,g$$  of $$CHC{l_3}$$  and $$40\,g$$  of $$C{H_2}C{l_2}$$  at the same temperature will be : ( Molecular mass of $$CHC{l_3} = 119.5\,u$$    and molecular mass of $$C{H_2}C{l_2} = 85\,u$$   )

A. $$90.92\,mm\,Hg$$  
B. $$115.0\,mm\,Hg$$
C. $$147.9\,mm\,Hg$$
D. $$285.5\,mm\,Hg$$
Answer :   $$90.92\,mm\,Hg$$
Solution :
$$\eqalign{ & {n_{CHC{l_3}}} = \frac{{25.5}}{{119.5}} = 0.213 \cr & {n_{C{H_2}C{l_2}}} = \frac{{40}}{{85}} = 0.47 \cr & {P_T} = P_A^ \circ {X_A} + P_B^ \circ {X_B} \cr & = 200 \times \frac{{0.213}}{{0.683}} + 41.5 \times \frac{{0.47}}{{0.683}} \cr & = 62.37 + 28.55 \cr & = 90.92 \cr} $$

Releted MCQ Question on
Physical Chemistry >> Solutions

Releted Question 1

An azeotropic solution of two liquids has boiling point lower than either of them when it

A. shows negative deviation from Raoult’s law
B. shows no deviation from Raoult’s law
C. shows positive deviation from Raoult’s law
D. is saturated
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Releted Question 2

For a dilute solution, Raoult’s law states that :

A. the lowering of vapour pressure is equal to the mole fraction of solute.
B. the relative lowering of vapour pressure is equal to the mole fraction of solute.
C. the relative lowering of vapour pressure is proportional to the amount of solute in solution.
D. the vapour pressure of the solution is equal to the mole fraction of solvent.
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Releted Question 3

When mercuric iodide is added to the aqueous solution of potassium iodide then

A. freezing point is raised.
B. freezing point is lowered.
C. freezing point does not change.
D. boiling point does not change.
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Releted Question 4

Which of the following $$0.1 M$$  aqueous solutions will have the lowest freezing point?

A. Potassium sulphate
B. Sodium chloride
C. Urea
D. Glucose
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