Question

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​

Answer 1

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

Further explanation

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

`\large {\boxed {\boxed {\bold {\Delta Tb \: = \: Kb.m}}}`

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