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Topic: A chemical test to distinguish between sulphurous acid and sulphuric acid.  (Read 9175 times)

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Offline kemensindia

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Sulphuric acid is an oxidising agent while sulphurous acid is a reducing agent. What could be a common test to distinguish between the two?

Offline Borek

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Re: A chemical test to distinguish between sulphurous acid and sulphuric acid.
« Reply #1 on: February 11, 2013, 07:50:15 AM »
You have to show your attempts at solving the question to receive help. This is a forum policy.
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Offline AWK

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Re: A chemical test to distinguish between sulphurous acid and sulphuric acid.
« Reply #2 on: February 11, 2013, 08:45:22 AM »
Sulphuric acid is an oxidising agent while sulphurous acid is a reducing agent. What could be a common test to distinguish between the two?
Only concentrated sulphuric acid shows oxidizing properties.
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Offline kemensindia

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Re: A chemical test to distinguish between sulphurous acid and sulphuric acid.
« Reply #3 on: February 11, 2013, 10:28:13 AM »
Sulphuric acid is an oxidising agent while sulphurous acid is a reducing agent. What could be a common test to distinguish between the two?
Since I would need a common reactant to react with with sulphurous acid as well as sulphuric acid, the reactant should be capable of getting, both, oxidised as well as reduced. I am unable to identify such a reactant to start with. Ferrous chloride came to my mind, since it can get oxidised to ferric chloride as well as get reduced to ferrous but i am not able to distinguish the different products with the reactions with sulphurous and sulphuric acid.

Offline Borek

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Re: A chemical test to distinguish between sulphurous acid and sulphuric acid.
« Reply #4 on: February 11, 2013, 10:35:10 AM »
Since I would need a common reactant to react with with sulphurous acid as well as sulphuric acid, the reactant should be capable of getting, both, oxidised as well as reduced.

No. Lack of reaction is a signal as well.
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Offline kemensindia

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Re: A chemical test to distinguish between sulphurous acid and sulphuric acid.
« Reply #5 on: February 11, 2013, 10:37:57 AM »
Sulphuric acid is an oxidising agent while sulphurous acid is a reducing agent. What could be a common test to distinguish between the two?
Would it be correct to say that sulphurous acid will react with ferric chloride to give ferrous chloride but there would be no reaction between sulphuric acid and ferric chloride.

Offline Borek

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Re: A chemical test to distinguish between sulphurous acid and sulphuric acid.
« Reply #6 on: February 11, 2013, 11:41:09 AM »
Would it be correct to say that sulphurous acid will react with ferric chloride to give ferrous chloride but there would be no reaction between sulphuric acid and ferric chloride.

Not bad, but I am not convinced ferric chloride is the best reagent to use. Color change is not that prominent, especially in the not too concentrated solutions.
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Offline kemensindia

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Re: A chemical test to distinguish between sulphurous acid and sulphuric acid.
« Reply #7 on: February 11, 2013, 08:58:30 PM »
Sulphuric acid is an oxidising agent while sulphurous acid is a reducing agent. What could be a common test to distinguish between the two?
Well I could not think of anything else. Can you suggest some reagent?

Offline Borek

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Re: A chemical test to distinguish between sulphurous acid and sulphuric acid.
« Reply #8 on: February 12, 2013, 06:39:57 PM »
Any oxidizing agent that changes its color when reduced should work.
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Offline kemensindia

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Re: A chemical test to distinguish between sulphurous acid and sulphuric acid.
« Reply #9 on: February 12, 2013, 10:09:38 PM »
Sulphuric acid is an oxidising agent while sulphurous acid is a reducing agent. What could be a common test to distinguish between the two?
Thanks a lot for your help.

Offline ajkoer

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Re: A chemical test to distinguish between sulphurous acid and sulphuric acid.
« Reply #10 on: February 24, 2013, 08:06:57 PM »
Carefully boil away part of the solution in a fume hood. For Sulfurous acid:

 H2SO3 <--> H2O + SO2 (g)

Distinct smell of SO2 and the solution's pH should decline. H2SO4 is more stable, should not observe a decline in pH.

Offline ajkoer

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Re: A chemical test to distinguish between sulphurous acid and sulphuric acid.
« Reply #11 on: February 26, 2013, 11:07:51 PM »
Carefully boil away part of the solution in a fume hood. For Sulfurous acid:

 H2SO3 <--> H2O + SO2 (g)

Distinct smell of SO2 and the solution's pH should increase (less acidic). H2SO4 is more stable, should not observe a rise in pH.

Offline AWK

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Re: A chemical test to distinguish between sulphurous acid and sulphuric acid.
« Reply #12 on: February 27, 2013, 02:55:59 AM »
Carefully boil away part of the solution in a fume hood. For Sulfurous acid:

 H2SO3 <--> H2O + SO2 (g)

Distinct smell of SO2 and the solution's pH should increase (less acidic). H2SO4 is more stable, should not observe a rise in pH.
This is not good advice. But wet indicator paper over test tube  after warming may work (H2SO4 in nonvolatile, SO2 with water forms acid). Note - this should be done after warming but not during warming.
AWK

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