Question

Sulphuric acid is 95.8% by mass . Calculate the mole fraction and molarity of H2SO4 of density 1.91 cm-3

Answer 1

Work with 1 L of solution 
density = mass / volume 
Thereform mass = density x volume 
mass 1 L solution = 1.329 g/ml x 1000 ml 
= 1329 g 
You know that there are 571.7 g of H2So4 in that 1 L 
So mass H2O = 1329 g - 571.7 g 
= 757.3 g H2O 
moles H2O = mass / molar mass 
= 757.3 g / 18.016 g/mol 
= 42.035 moles H2O 
moles H2SO4 = 571.7 g / 98.076 g/mol 
= 5.829 moles 
total moles in solution = 42.035 mol + 5.829 mol = 47.864 mol 
mole fraction H2SO4 = 5.829 mol / 47.864 mol 
= 0.12178 
= 0.1218 (4 sig figs) 
Molrity = moles solute / litres solution 
M H2SO4 = 5.829 mol / 1.000 L 
= 5.829 M