Solutions are made that contain 0.1 moles of each of the following compounds below in 100 g of H2O. Choose the compound whose solution will have the lowest freezing point.
NaBr
MgCl2----
KClO3
CO2
MgSO4
I know the answer is MgCl2
but I don't know how to get it. I know I have to use a periodic table but don't see the solution please explain
The secret is remembering a little emphasized point when these problems are worked. That point is---"the extent to which these thing happen depends SOLELY on the number of dissolved particles."
So how many particles do we get when NaCl dissolves.
NaCl ==> Na^+ + Cl^- = 2.
MgCl2 ==> Mg^+2 + 2Cl^- = 3
KClO3 ==> K^+ + ClO3^- = 2
CO2 ==> doesn't dissolve to an appreciable extent and what little dissolves doesn't produce many ions so let's call this zero.
MgSO4 ==> Mg^+2 + SO4^-2 = 2
So which one produces the largest number of particles (all of them are the same molality). That would be MgCl2.
Ah, the quest to find the compound with the lowest freezing point! Let's dive into it, shall we?
When it comes to determining the freezing point depression, we need to consider the number of particles that each compound will dissociate into when dissolved in water. This is because the more particles there are in a solution, the greater the freezing point depression.
If we take a look at the compounds, we can see that NaBr, KClO3, CO2, and MgSO4 will dissociate into two particles when dissolved in water. However, MgCl2 will dissociate into three particles.
Here's why:
NaBr dissociates into Na+ and Br-.
KClO3 dissociates into K+ and ClO3-.
CO2 dissociates into CO3- and O2-.
MgSO4 dissociates into Mg2+ and SO4(2-).
But when MgCl2 dissolves, it forms three particles: Mg2+ and two Cl- ions.
Therefore, MgCl2 will have the highest freezing point depression among all these compounds since it dissociates into the most particles. Hence, it will have the lowest freezing point.
I hope that clears things up, and I apologize for any confusion caused by my clownish explanation.
To determine which compound will have the lowest freezing point, we need to calculate the van't Hoff factor (i) for each compound. The van't Hoff factor represents the number of particles that a compound will dissociate into when it is dissolved in a solution.
The van't Hoff factor can be determined using the following equation:
i = (1 + n), where n is the number of ions that the compound dissociates into.
For each compound:
1. NaBr: This compound dissociates into Na+ and Br- ions when dissolved in water. So, the van't Hoff factor for NaBr is:
i = (1 + 2) = 3
2. MgCl2: This compound dissociates into Mg2+ and 2Cl- ions when dissolved in water. So, the van't Hoff factor for MgCl2 is:
i = (1 + 3) = 4
3. KClO3: This compound dissociates into K+ and ClO3- ions when dissolved in water. So, the van't Hoff factor for KClO3 is:
i = (1 + 2) = 3
4. CO2: This compound does not dissociate into ions when dissolved in water. So, the van't Hoff factor for CO2 is:
i = 1
5. MgSO4: This compound dissociates into Mg2+ and SO42- ions when dissolved in water. So, the van't Hoff factor for MgSO4 is:
i = (1 + 2) = 3
Now, we know that the solution with the lowest freezing point will have the highest van't Hoff factor. In this case, MgCl2 has the highest van't Hoff factor of 4, indicating that it will have the lowest freezing point when dissolved in water.
To determine which compound will have the lowest freezing point, we need to look at the concept of freezing point depression. Freezing point depression occurs when a solute is added to a solvent, causing the freezing point of the solution to be lower than the freezing point of the pure solvent.
In this case, we are comparing the freezing point depressions caused by adding 0.1 moles of each compound to 100 g of water. To determine the compound with the lowest freezing point, we need to consider the number of particles each compound will produce when it dissociates or dissolves in water.
First, let's determine the number of particles each compound will produce:
- NaBr will dissociate into Na+ and Br- ions, so it will produce 2 particles.
- MgCl2 will dissociate into Mg2+ and 2Cl- ions, so it will produce 3 particles.
- KClO3 will dissociate into K+ and ClO3- ions, so it will produce 2 particles.
- CO2 will dissolve in water to form H2CO3, so it will produce 1 particle.
- MgSO4 will dissociate into Mg2+ and SO4^2- ions, so it will produce 3 particles.
According to the colligative properties of solutions, the freezing point depression is directly proportional to the number of particles produced. Therefore, the compound that produces the highest number of particles will have the lowest freezing point.
Since MgCl2 produces the highest number of particles (3 particles), its solution will have the lowest freezing point among the given compounds.