Question

Calculate the Molality of sulphuric acid solution in which mole fraction of water is 0.85 ?

Answer 1

The molal concentration is 9.8 mol/kg.

Explanation:

If the mole fraction of water is 0.85, the mole fraction of sulfuric acid is 0.15.

So, we can express the concentration as

`"0.15 mol sulfuric acid"/"0.85 mol water"`

Convert moles of water to kilograms of water

`"Mass of water" = 0.85 color(red)(cancel(color(black)("mol H"_2"O"))) × (18.02 color(red)(cancel(color(black)("g H"_2"O"))))/(1 color(red)(cancel(color(black)("mol H"_2"O")))) × (1 "kg H"_2"O")/(1000 color(red)(cancel(color(black)("g H"_2"O")))) = "0.0153 kg H"_2"O"`

Calculate the molal concentration of the water

`b = "0.15 mol sulfuric acid"/"0.0153 kg water" = "9.8 mol/kg"`