Lowering of vapour pressure due to a solute in `1` molal aqueous solution at `100^(@)C` is
a.`13.44 mm Hg` ,b. `14.14 mm Hg` ,c.`13.2 mm Hg` ,d. `35.2 mm Hg`

Options

A. 13.44 mm Hg
B. 14.12 mm Hg
C. 31.2 mm Hg
D. 35.2 mm Hg

Answer

A

Explanation

`p = p_(A) + p_(B)`
`p = p_(A)^(@) x_(A) + p_(B)^(@) x_(B)`
`= 120 xx (2)/(4) + 80 xx (2)/(4)`
`= 60 + 40 = 100` torr
`y_(B) =` mole fraction of B in the vapour phase
`= (p_(B))/(p_("total")) = (40)/(100) = (2)/(5)`