Question

Match the boiling point with `K_(b)` for `x,y` and `z`, if molecular weight of `x,y` and `z` are same.
`{:(,b.pt,,k_(b),),(x,100,,0.68,),(y,27,,0.53,),(z,253,,0.98,):}`

Answer 1

We know,
`K_(b)=(RT_(b)^(2))/(1000l_(v))=(RT_(b)^(2).M)/(1000 DeltaH_(v))=(RT_(b).M)/(1000 DeltaS_(v))`
`(DeltaS_(v)=(DeltaH_(v))/(T_(b)))`
Since during vaporisation entropy increases because randomnes increase. Also `DeltaS_(v)` may be taken as almost constant beacuse for, liquid`hArr` vapour even if the extent of disorderness varies from liquid to liquid beacuse the `S_(v)` is abnormally higher than `S_(v)-S_(t)=DeltaS_(v)` is almost constant. If `M` and `R` are constant `K_(b)propT_(b)`.
or `K_(b)(x)=0.68, k_(b)(y)=0.53`
and `K_(b)(z)= 0.98`