What is the effect of the van't Hoff factor on the boiling point elevation or freezing point depression for a given electrolytic solution?

Well, usually #i >=1#, so in many cases, it will accentuate the boiling point elevation or freezing point depression from the pure solvent.

For non-electrolytes, we would normally write

#DeltaT_f = T_f - T_f^"*" = -K_fm# #" "bb((1))#

#DeltaT_b = T_b - T_b^"*" = K_bm# #" "" "bb((2))#

where:

• #T_f# and #T_b# are the freezing and boiling points, respectively, of the solution. #"*"# indicates pure solvent.
• #K_f# and #K_b# are the freezing point depression and boiling point elevation constants, respectively, of the solvent.
• #m# is the molality of the solution in #"mol solute/kg solvent"#.

When we account for electrolytes, i.e. those substances that dissociate in solution, we write in the van't Hoff factor #i# to account for the effective number of solute particles per formula unit:

#DeltaT_f = T_f - T_f^"*" = -color(red)(uli)K_fm# #" "bb((1"'"))#

#DeltaT_b = T_b - T_b^"*" = color(red)(uli)K_bm# #" "" "bb((2"'"))#

And thus, #i >= 1# for typical electrolytes, increasing the magnitude to which the boiling points increase and freezing points decrease.