Question

Which of the following would have the highest boiling point?

a) 0.10m Cr2(SO4)3

b) 0.15m Zn (CH3COO)2

c) pure H2O

d) 0.35m CH4N2O

e) 0.16m BaI2

Answer 1

We have to know few assumptions before solving this actual problem,
(i) The solvent used to dissolve this solutes given is water (ii) molality is same as molarity because
Molality = moles of solute / Kg of water and for molarity this kg of water becomes 1L solution
roughly equivalent to 1gm/1mL.
ΔT_b = i *m*K_b
a) ΔT_b = 0.512 * 0.10*5 = 0.256^oC
b)  ΔT_b = 0.512 * 0.15*3 = 0.2304^oC
c) molarity of pure water = 55.5 M
   ΔT_b = 0.512 * 55.5*2 = 56.832^oC
d)  ΔT_b = 0.512 * 0.35 * 1 = 0.1792^oC
e) ΔT_b = 0.512*0.16*3 = 0.24576^oC
From all the above values it is clear that pure water has the highest boiling point, option c)