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Help me Plz

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Chemistry
October/November 2003
Paper 3
5th question C(ii)

I am not able to understand the mark scheme

someone help me plz
THANKS
 
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Well, I am going to paste the question over here.

To aqueous sulphur dioxide, acidified barium chloride solution is added. The mixture
remains clear. When bromine is added, a thick white precipitate forms. What is the
white precipitate? Explain why it forms.

Now the first part of the question is asking what is the substance formed when Aqueous sulphur dioxide reacts with bromine.
Here you have to apply your basic knowledge about chemical reaction, as we know that when barium reacts with sulphur dioxide we will obtain
Barium Sulphate, which is the first answer.

Moving on, the next part of the question asks, what is and why is the white precipitate forming?
Now you need to look at the chemical reaction further, finding out all the products made. We know that there are sulphate ions, as previously said, and so if you remind your self of the test for sulphates they involve giving a white precipitate after mixing with a barium salt. And so this is what has happened here with Barium Sulphate. This is due to the fact that barium sulphates have oxidised or reacted with sulphur dioxide giving sulphate ions.

Hope you understood, let me know if you need any further clarification.
 
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Barium sulphate reacted with sulphur dioxide to give sulphate ions????
How??
Can u give an example of a reaction??
 
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THE PRECIPITATE IS BARIUM SULPHATE, SULPHUR DIOXIDE IS OXIDISED BY BROMINE INTO SULPHATE IONS
 
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Dude, this answer is written in mark scheme i know that
can u explain this sentence more further by writing a reaction ????
:p
 
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The Question is about testing for anions in solution.
First When u have a sulphuric acid u want to test its ion. u must memorize this test. You must add or make the sulphuric acid react with barium chloride solution and dilute hydrochloric acid. If a white precipitate is formed then sulphate ions are present.
You simply just memorize testing for anions in a solution. There is no equations about it just tests.
 
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I didnt understand the thing sulphur dioxide is oxidised by bromine into sulphate ions :(
This is actually written in marking scheme and by writting this u would gain a mark.
so plz help me :)
 
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