[Violet89]

The extent of fragmentation for ionic compounds can be derived by comparing the molality expected if no dissociation with what is actually obtained from experiment. When 0.278 g of K3Fe(CN)6 (molar mass 329.25 g/mol) is dissolved in 100.0 g of water, the freezing point is found to be -0.070 °C. How many ions are present for each formula unit of K3Fe(CN)6 dissolved? (Kf for water is 1.86 K/m).

The answer is 5.

In water, the complex salt dissociates: K4Fe(CN)6 ==> 4K^+ + Fe(CN)6^-4

When K4Fe(CN)6 dissociates in water, there are 5 ions. Is this all I need to know for this problem, or these types of problems when asking for ions present? I'm confused. I'd appreciate any help. :-)

[Hunter2]

What you talking about? In beginning its K₃[Fe(CN)₆] and below its  K₄[Fe(CN)₆].

[Violet89]

What you talking about? In beginning its K₃[Fe(CN)₆] and below its  K₄[Fe(CN)₆].

Oops, yes, it's supposed to be 4 in the problem. That's what I'm talking about...

[Borek]

You should use the information given to calculate Van 't Hoff factor.

[Violet89]

You should use the information given to calculate Van 't Hoff factor.

Thanks.