Home
Class 12
CHEMISTRY
An aqueous solution freezes at 272.4 K w...

An aqueous solution freezes at 272.4 K while pure water freezes at 273 K. Given `K_(f)=1.86 K kg "mol"^(-1)`,`K_(b)=0.512 K kg "mol"^(-1)` and vapour pressure of water at 298 K = 23.756 mm Hg. Determine the following.
Lowering in vapour pressure at 298 K is

A

`0.13`

B

`0.15`

C

`0.16`

D

`0.1378`

Text Solution

Verified by Experts

The correct Answer is:
D
Lowering in vapour pressure
According to Raoult's law
`(P^(@)-P)/P^(@)=chi_(B)`
Now, `chi_(B)=n_(B)/(n_(A) xx n_(B))=n_(B)/n_(A)` (for dilute solution)
=`n_(B)/(W_(B)) xx Mw_(A)` ….(i)
and m=`n_(B) xx 1000/W_(A)` ….(ii)
Dividing Eq. (i) by Eq. (ii), we get
`chi_(B)/m=(Mw_(A))/1000 rArr chi_(B)=(m xx Mw_(A))/1000`
`:. chi_(B)=(0.322 xx 18)/(1000)=0.00580`
Now `(P^(@)-P)/P^(@)=0.00580`
or `P^(@)-P=P^(@) xx 0.00582 = 23.756 xx 0.00580`
`=0.1378 mm`
`:.` Lowering in vapour pressure =0.1378 mm
Promotional Banner

Similar Questions

Explore conceptually related problems

An aqueous solution freezes at 272.4 K while pure water freezes at 273 K. Given K_(f)=1.86 K kg "mol"^(-1) , K_(b)=0.512 K kg "mol"^(-1) and vapour pressure of water at 298 K = 23.756 mm Hg. Determine the following. Boiling point of the solution is

An aqueous solution freezes at 272.4 K while pure water freezes at 273 K. Given K_(f)=1.86 K kg "mol"^(-1) , K_(b)=0.512 K kg "mol"^(-1) and vapour pressure of water at 298 K = 23.756 mm Hg. Determine the following. Molality of the solution is

An aqueous solution freezes at 272.4 K while pure water freezes at 273 K. Given K_(f)=1.86 K kg "mol"^(-1) , K_(b)=0.512 K kg "mol"^(-1) and vapour pressure of water at 298 K = 23.756 mm Hg. Determine the following. Depression in freezing point of solution

AN aqueous solution of a substacne freezes at -0.186^(@)C. The boiling point of the same solution (k _(f) =1.86 Km^(-1), K_(b)=0.512 Km^(-1)) is :

An aqueous solution at freezes at -2.55^(@)C . What is its boiling point (K_(b)^(H_(2)O)=0.52 K m^(-1) , K_(f)^(H_(2)O)=1.86 K m^(-1) ?

A solution of non-volite solute in water freezes at -0.30^(@)C .The vapour pressure of pure water at 298 K is 23.51 mm Hg .and K_(f) for water is 1.86 degree per molal. Calculate the vapour pressure of this solution at 298 K .

A solution of a non-volatile solute in water freezes at -0.30^(@)C . The vapour pressure of pure water at 298 K is 23.51 mm Hg and K_(f) for water is 1.86 degree//molal . Calculate the vapour pressure of this solution at 298 K .

After adding non-volatile solute freezing point of water decreases to -0.186^(@)C . Calculate Delta T_(b) if K_(f)=1.86 " K kg mol"^(-1) and K_(b)=0.21 "K kg mol"^(-1) .