Question

what is the mass % in an aqueous solution that has a mole fraction of K2SO4, X=0.350?

83.9% or 5.27%?

Answer 1

Mole fraction of K2SO4 = 0.35

Mole fraction of water = 1-0.35 = 0.65

Let X = number of moles of K2SO4

Y = number of moles of water

X/(X+Y) = 0.35 ---> X = 0.35 X + 0.35 Y ---> X = 0.54 Y

Mol wt of K2SO4 = 174.25 g

Mol wt of water = 18

Wt of K2SO4 / Mol wt of K2SO4 = 0.54 * (wt of water / mol wt of water)

Wt of K2SO4 / wt of water = 0.54 *(174.25/18) = 5.23

Mass % of K2SO4 = (wt of K2SO4 / wt of K2SO4 + wt of H2O)*100

=( 5.23 / 6.23 )*100 = 83.94 %

Mass % of K2SO4 in aqueous solution = 83.94%