Which of the given solutions should display the GREATEST departure from the freezing point, and the boiling point of the water solvent?

#A.# #LiCl(aq)#
#B.# #NaCl(aq)#
#C.# #"sucrose"(aq)#
#D.# #Na_3PO_4(aq)#
#E.# #MgBr_2(aq)#

1 Answer
anor277
Jan 30, 2017

Probably #D# if EQUAL, formal concentrations of each salt were prepared.

Explanation:

The more particles in solution, the greater the #"freezing point depression"#, and the greater the #"boiling point elevation"#

All these solutes speciate in aqueous solution to give a number of different particles:

#A.# #LiCl(s)rarr Li^+ + Cl^-#

#B.# #NaCl(s)rarr Na^+ + Cl^-#

#C.# #"sucrose"(s)rarr "sucrose"(aq)#

#D.# #Na_3PO_4(s) + H_2O rarr 3Na^(+) + HPO_4^(-) + HO^-#

#E.# #MgBr_2(s)rarr Mg^(2+) + 2Br^-#

Clearly the phosphate ion delivers the most species, the most ions, in aqueous solution. And thus this species should give the greatest #"boiling point elevation"#.

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