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Misplaced Homework Thread

- Homework Statement
- "An aqueous solution, with 5% of CaX_2 (X is an halogen), freezes at t=-1.396°C. K_cr=1.860. Find X."

- Relevant Equations
- $$\Delta t = K_{cr}\cdot m \cdot i$$

I can't find my mistake, can you help me?

I suppose that in 1000g of solution there are 50g of solute and 950g of solvent.

Then I find the molality

$$m= \frac{50}{MM} \cdot \frac{1}{0.950}$$

So I can find the Molar Mass of the compound using the relation $$\Delta t=K_{cr}\cdot m \cdot i$$ where i is the van 't Hoff coefficient which is 3 in this case.

At the end I don't find an halogen (Rubidium is the closest) so I assume something is wrong but I can't see what.

I suppose that in 1000g of solution there are 50g of solute and 950g of solvent.

Then I find the molality

$$m= \frac{50}{MM} \cdot \frac{1}{0.950}$$

So I can find the Molar Mass of the compound using the relation $$\Delta t=K_{cr}\cdot m \cdot i$$ where i is the van 't Hoff coefficient which is 3 in this case.

At the end I don't find an halogen (Rubidium is the closest) so I assume something is wrong but I can't see what.

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