The temperature at which molarity of pure water is equal to its molality
A. `273K`
B. `298K`
C. `277K`
D. none of these
A. `273K`
B. `298K`
C. `277K`
D. none of these
Correct Answer – C
Molality and mole fraction are related as follows:
`m = (x_(B) xx 1000)/((1 – x_(B)) m_(A))`
`1 = (x_(B) xx 1000)/((1 – x_(B)) xx 18)`
[ `m = 1 x_(B) =` mole fraction of solute `m_(A)=` molar mass of solvent]
`x_(B) = 0.0176, ” ” x_(A) = 0.9824`
`p = p_(0) x_(A)`
`p = 760 xx 0.9824`
`= 746.624`
`Delta p = P_(0) – p = 760 – 746.624`
`~~ 13.4` mm Hg
Correct Answer – C
At `4^(@)C (277K)` density of water is `1g cm^(-3)`
`:. 1000 cm^(3)` of water `= 1000g` of water.
`:.` At 277 K molality of pure water is same as its molarity (55.56).