Question

Which aqueous solution has the lowest boiling point?

0.10 m C6H12O6

0.10 m NaCl

0.10 m AlCl3

0.10 m BaCl2

Answer 1

According to colligative properties,:

dTb = Kb*m*i

where:

dTb increase in boiling point

Kb = constant for BP increase for water alone,

m = molality of mix, i.e. mol of solute / kg of solvent

i = total ions in solution

from the data given

dTb = m*i*Kb

Kb, m are constant, so only "i" number of ions matter for th estud

ignore glucose, since it is moleuclar, i = 1

NaCl = 2 ions, i = 2

AlCl3 = Al+3 + 3Cl- = 1+3 = 4 ions

BACl2 = 3 ions, Ba+2 + 2Cl- = 1+2 = 3

therefore

AlCl3 must have the HIGHEST point

and

glucose must have the LOWEST point

therefore

Choose C6H12O6, since will be much lower than all other salts