Concentration questions about freezing point depression and osmolarity?

Question

#A)# Will glucose or fructose have the greater freezing point depression?
#B)# What are the osmolarities of #"0.10 M NaCl"# and #"0.080 M Na"_2"SO"_4#?

Jeremiah Adams · Accepted Answer

#A)# Well, don't fructose and glucose have the same molar mass? Not that it matters...

#DeltaT_f = T_f - T_f^"*" = -iK_fm#

In principle, it doesn't matter what the identity of the compound even is...

That is the whole idea behind colligative properties. Under the general chemistry approximation, as long as it dissociates to produce the same number of particles in solution... #DeltaT_f# is the same.

Hence, they have the same freezing point at the same concentration.

#B)# Osmolarity is analogous to molarity, and treats the dissociated particles on the same footing.

#"NaCl"(aq) -> "Na"^(+)(aq) + "Cl"^(-)(aq)#

As #"Na"^(+)# and #"Cl"^(-)# go into solution, #"0.10 M"# #"NaCl"# is then...

#ul"0.20 Osm/L"#.

#"Na"_2"SO"_4(aq) -> 2"Na"^(+)(aq) + "SO"_4^(2-)(aq)#

#"0.080 M"# Sodium sulfate, #"Na"_2"SO"_4#, has three times the osmolarity as what is shown for its molarity, and it thus is...

#ul"0.240 Osm/L"#

Xavier Avery · Answer

undefined Certainly, feel free to ask your concentration-related questions about freezing point depression and osmolarity.

Concentration questions about freezing point depression and osmolarity?

#A)# Will glucose or fructose have the greater freezing point depression? #B)# What are the osmolarities of #"0.10 M NaCl"# and #"0.080 M Na"_2"SO"_4#?

#A)# Will glucose or fructose have the greater freezing point depression?
#B)# What are the osmolarities of #"0.10 M NaCl"# and #"0.080 M Na"_2"SO"_4#?