Assuming equal concentrations, rank these aqueous solutions by their freezing point.?
K2CO3, Li3PO4, Sn(ClO3)4, NH4I
I tried to rank them according to the number of ions but i can't get it.
highest freezing point --> lowest freezing point
Sn(ClO3)4 -> Li3PO4 -> K2CO3 -> NH4I but this wasn't correct. please help!
if anyone knows what it could be please help!
The solution with the greatest freezing-point depression, ΔTf, will have the lowest freezing point. Freezing-point depression is directly proportional to the total particle concentration. You need to compare the ions per formula unit.
From highest to lowest the order is...
NH4I, K2CO3, Li3PO4, and Sn(ClO3)4
NH4l has the lowest total particle concentration, the lowest ΔTf, and the highest (least negative) freezing point. Sn(NO3)4 has the highest total particle concentration, the highest ΔTf, and the lowest (most negative) freezing point.
Why? Just compare the ions per formula unit. The ones with more ions have a lower freezing point and the ones with less ions have a greater freezing point. Trust me :) You just have to reverse your answers. The answer should be (from highest to lowest):
NH4I, K2CO3, Li3PO4, and Sn(ClO3)4
You reversed them....the one with the greater ions have a lower freezing point and the ones with less ions have a greater freezing point.
Let me know if this is correct :]
it was correct! what an unfortunate mistake =/ thanks for explaining it!
Anytime! Glad to have helped.
To rank these aqueous solutions by their freezing point, you need to consider the concept of colligative properties. Freezing point depression is one such colligative property, which depends on the number of solute particles present in a solution.
In this case, you are correct in considering the number of ions as an important factor. However, you should also take into account the dissociation of the solute in water.
Let's break it down:
1. K2CO3: This compound dissociates into three ions when dissolved in water: 2 K+ ions and 1 CO3^2- ion. So, the effective number of particles in solution is 3.
2. Li3PO4: This compound dissociates into four ions when dissolved in water: 3 Li+ ions and 1 PO4^3- ion. The effective number of particles in solution is 4.
3. Sn(ClO3)4: This compound dissociates into nine ions when dissolved in water: 4 Sn^4+ ions and 4 ClO3^- ions. The effective number of particles in solution is 9.
4. NH4I: This compound dissociates into two ions when dissolved in water: 1 NH4+ ion and 1 I^- ion. The effective number of particles in solution is 2.
Now, considering that freezing point depression is directly related to the number of particles, the aqueous solution with the highest freezing point will have the fewest number of particles. This means that NH4I will have the highest freezing point.
Ranking them from highest to lowest freezing point:
NH4I > K2CO3 > Li3PO4 > Sn(ClO3)4
So, NH4I has the highest freezing point and Sn(ClO3)4 has the lowest freezing point.