# chemistry

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20) The ideal value of i (van't Hoff factor) for (NH4)3PO4.
A) 2 B) 5 C) 4 D) 3 E) 1

I know the answer but how are problems like this figured out?

• chemistry -

You look at how they ionize.
(NH4)3PO4 ==> 3NH4^+ + PO4^-3
So that's 4 particles.
NaCl is 2.
CsCl = 2
BaCl2 = 3
Ba3(PO4)2 = 5
C12H22O11(sucrose; i.e., table sugar) = 1 since it dissolves BUT doesn't ionize.
Glucose, C6H12O6 = 1

• chemistry -

In these questions, we are not concerned that which compound it is. The only thing which matter is that how they ionise because it is the number of particles that we are concerned about. That's why these are called collimating properties. So 1 molecule of NaCl gives 1 Na atom and 1 Cl atom in water. So, it's vant hot factor (i) = 2.

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