Question

Which of these solutes raises the boiling point of water the most?
ionic lithium chloride (LiCl)
ionic sodium chloride (NaCl)
molecular sucrose (C12H22O11)
ionic sodium phosphate (Na3PO4)
ionic magnesium bromide (MgBr2)

Answer 1

I think the answer would be Ionic sodium phosphate (Na3PO4) because it has the greatest boiling point elevation.

Answer 2

Answer: ionic sodium phosphate $(Na_3PO_4)$

Explanation:

The formula used:

$\Delta T_b=i\times k_b\times m$

$\Delta T_b$= change in boiling point

i = Van'T Hoff factor  

$k_b$ = boiling point constant

m = molality

1.  For $LiCl$

$LiCl\rightarrow Li^{+}+Cl^{-}$  

i= 2 as it is ionic and dissociate to give 2 ions.

2. For $NaCl$

$NaCl\rightarrow Na^{+}+Cl^{-}$  

i= 2 as it is ionic and dissociate to give 2 ions.

3. For $C_{12}H_{22}O_{11}$

, i= 1 as it is a non electrolyte and does not dissociate.

4. For $Na_3PO_{4}$

$Na_3PO_4\rightarrow 3Na^{+}+PO_4^{3-}$  

, i= 4 as it is ionic and dissociate to give 4 ions.

5.  For $MgBr_{2}$

$MgBr_2\rightarrow Mg^{2+}+2Br^-$  

, i= 3 as it is ionic and dissociate to give 3 ions.

Thus as vant hoff factor is highest for $Na_3PO_{4}$ , the boiling point will be raised most.