Question

The density of solution is heigher than 1 then relationship between molarity and molality is

Answer 1

Relation ship between Molarity (M) and Molality (m)

let moles os solid = nB

M = nB / V (in ml) x 1000

D(soln) = mass (soln) / V (soln)

Mass of solution = Density x Volume

d x 1000

[ Let assume of soln = 1000ml ]

M = nB / V (in ml) x 1000

M = WB / M wtB x 1000 / 1000 [ M = nB / 1000 x 1000 = nB ]

M = WB / MwtB

WB = M x MwtB

wt of solvent = wt of soln -- wt of solute

= 1000d -- M . MwtB

Molality (m) = nB / WA (gm) x 1000

m = M / 1000d -- M x MwtB x 1000 ( M = No. of moles of solute )

Here,

A = Solvent

B = Solute