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Topic: Adding carbon powder... why? (Acid and Base, Titration)  (Read 2227 times)

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Adding carbon powder... why? (Acid and Base, Titration)
« on: July 24, 2012, 08:39:53 AM »
Hello Chemists!

I have a problem here... I am going through some old stuff in chemistry and I have found a lab instruction for titration.
I will write what it says:

1. Pour 25cm^3 Sodium Hydroxide into the conical flask
2. Add 3-4 drops of BTB and a magnet
3. Put the flask on a magnetic stirrer
4. Fit a burette to a clamp stand and fill it with HCl
5. Add HCl to the solution in the conical flask until it is neutralized.
6. Add a teaspoon of carbon powder and swirl the flask
7. Remove the carbon by filtering into a crystalizing dish..
8. Done...

Ok, So what happens if I add some carbon powder? And why is it important to do it? Please, reply me :D

Offline fledarmus

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Re: Adding carbon powder... why? (Acid and Base, Titration)
« Reply #1 on: July 24, 2012, 08:56:14 AM »
It sounds like you are removing the bromothymol blue from the solution. I'm not sure why you would be doing that though, unless you were planning on using the solution for something else. What do you do with the solution after it is neutralized and filtered?

Activated charcoal or decolorizing carbon were once used very extensively for removing trace amounts of highly colored materials from solutions. Highly colored materials generally have conjugated double bond systems and benzene rings which are strongly absorbed by the graphite sheet structure of the carbon and precipitated from the solution. If your original sample contained only sodium hydroxide and BTB, and you neutralized it with HCl, your final solution should have only sodium chloride (salt) and BTB. Precipitating the BTB out with carbon would leave only salt water.

Just my guess...

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