Why can't hexane or toluene solutions dissolve in aqueous bromine?

In summary: Red indicates dissociation of an ion into two or more atoms. In this case, the Br was dissociating into bromine and hydrogen.
  • #1
redpower
1
0
I have just carried out a lab experiment today and desperately need some help!

1. The Experiment:

In my experiement I attempted to mix a solution of hexane with aqueous bromine. I started off by adding 15 drops of bromine into a test tube and then added 7 drops of hexane ontop of that. Prior to shaking, I could see two distinct colours in the test tube separated by a meniscous: the yellow bromine liquid lied at the bottom and the clear + colourless hexane solution lied on top of the bromine. After shaking, something odd happened. The two layers switched places => bromine ended up on top and hexane resided at the bottom of the test tube. The two colours were still distinct and separated by a meniscous. (The same thing happened when I tried to mix toluene with bromine)


2. What I discovered

Seeing that these two solutions would not dissolve each other, I concluded that one of them must be polar and the other must be non-polar. (We have previously learned that only "like dissolves like") HOWEVER, after analysing the substances, I realized that hexane (a hydrocarbon) and bromine are BOTH NON-POLAR SUBSTANCES. If that is the case, they should have dissolved each other - but they didn't! Thus, I am in a dilemma right now and have no idea how to approach this lab.

Any help would be greatly appreciated! Thank you in advance!
 
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  • #2
Aqueous bromine is bromine dissolved in a water based solution. Usually HBr and H20. Your bromine preparation did not mix with either hexane or toluene because of their non-polar nature. They are non-miscible with water. Gaseous bromine, either Br2(g) or HBr(g), would dissolve however.
 
  • #3
MrCoffee2004 said:
Aqueous bromine is bromine dissolved in a water based solution. Usually HBr and H20.

HBr in bromine solution? Some amount being produced in disproportionation - for sure, but this is not the main form of Br2 present.
 
  • #4
I don't think that is right. If it were, the Br2 would have dissolved into the hexane or toluene. The Br was in an ionic state in the aqueous solution and that is why it didn't dissolve.
 
  • #5
If it was ionic, how come solution was red?
 

1. Why can't hexane or toluene solutions dissolve in aqueous bromine?

Hexane and toluene are non-polar solvents, meaning they do not have a positive or negative charge. Aqueous bromine, on the other hand, is a polar solvent, meaning it has a positive and negative charge. Polar solvents are only able to dissolve other polar solvents, while non-polar solvents can only dissolve other non-polar solvents. This is due to the principle of "like dissolves like", where substances with similar polarity are able to mix together.

2. Can any other solvent dissolve aqueous bromine?

Yes, other polar solvents such as water, alcohols, and ethers are able to dissolve aqueous bromine. These solvents have a similar polarity to aqueous bromine and are able to form strong intermolecular bonds with it, allowing them to mix together and form a solution.

3. Are there any ways to make hexane or toluene solutions dissolve in aqueous bromine?

Yes, there are a few ways to make hexane or toluene solutions dissolve in aqueous bromine. One method is to add a small amount of a polar co-solvent, such as acetone or ethanol, to the solution. This will help to bridge the gap between the polar and non-polar solvents, allowing them to mix together. Another method is to increase the temperature of the solution, which can increase the solubility of non-polar solvents in polar solvents.

4. Why is it important to understand solubility of different solvents?

Understanding solubility is important in various scientific fields, such as chemistry and biology. It helps us to predict how different substances will interact with each other and how they will behave in a solution. For example, understanding the solubility of different solvents is crucial in drug development, as it can impact the effectiveness and absorption of a medication in the body.

5. Is there any practical application for the fact that hexane or toluene solutions cannot dissolve in aqueous bromine?

Yes, this concept has practical applications in industries such as oil and gas, where non-polar solvents are used to extract and separate hydrocarbons from crude oil. In this case, the non-polar solvent is able to dissolve the hydrocarbons, while the polar water is able to dissolve other impurities, allowing for a more efficient separation process. Understanding the solubility of different solvents also has applications in environmental science, as it can help to predict how pollutants will behave in different environments.

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