Question

The molarity of a solution of sulpuric acid is 1.35M .calculate its molality.density of acid solution is 1.02g/cm^3

Answer 1

Molarity is no. of moles present in 1 litre of solution,
therefore we havs 1.35 moles in 1 lit of solution
as density of solution is given hence we can calculate the mass of 1 lit solution = 1002 gm

now molality is no. of moles in 1 kg of solvent
now we don't have mass of solvent....

but we know the mass of 1 lit solution
and mass of solute in 1lit solution which is = 98 * 1.35 i. e. 132.3 gm

mass of solvent in 1 lit solution = 1002 - 132.3=869.7 gm

now use unitary 869.7 gm contains 1.35 moles of solute
hence 1000 gm solvent will contain (1.35 * 1000)/869.7 which is equal to 1.55

Hope, it may help
I personally don't believe in that formula that's why I solve it by their usual meaning

ignore calculation mistake if present....
Thank you...