Which of the following aqueous solutions has the highest boiling point? A) 0.10 M lithium sulfate, Li2SO4
B) 0.10 M hydrochloric acid, HCI
C) 0.10 M lithium nitrate, LINO3
D) 0.10 M magnesium sulfate, MgSO4

The highest boiling point : A) 0.10 M lithium sulfate, Li₂SO4

Solutions from volatile substances have a higher boiling point and lower freezing points than the solvent  

ΔTb = Tb solution - Tb solvent  

ΔTb = boiling point elevation  

Kb = molal boiling point increase  

m = molal solution  

For electrolyte solutions there is a van't Hoff factor = i  

i = 1 + (n-1) α  

n = number of ions from the electrolyte  

α = degree of ionization, strong electrolyte α = 1, for non electrolytes i = 1  

So ΔTb   ≈ i(van't Hoff), the greater i, the greater ΔTb

α = 1 ,  strong electrolyte

A) 0.10 M lithium sulfate, Li₂SO4

Li₂SO4 ⇒2Li⁺+SO₄²⁻ ⇒n=3

B) 0.10 M hydrochloric acid, HCI

HCl⇒H⁺+Cl⁻⇒n=2

C) 0.10 M lithium nitrate, LINO₃

LINO₃ ⇒ Li⁺+NO₃⁻ ⇒n=2

D) 0.10 M magnesium sulfate, MgSO4

MgSO4 ⇒ Mg²⁺ + SO₄²⁻ ⇒ n=2