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Which is the best way to distinguish between aqueous solutions of sodium carbonate and...

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phanpal999 | Student, Grade 8 | Salutatorian

Posted September 12, 2013 at 1:02 PM via web

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Which is the best way to distinguish between aqueous solutions of sodium carbonate and ammonium carbonate and why?

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llltkl | College Teacher | Valedictorian

Posted September 12, 2013 at 1:32 PM (Answer #1)

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Ammonium carbonate decomposes upon heating in aq. solution to produce carbon dioxide and ammonia, the latter gas can be identifed from its characteristic odour and also by using a moist red litmus paper. Red litmus turns to blue when it comes in contact with ammonia. The balanced chemical reaction for the decomposition is:

`(NH4)2CO3 (s) rarr CO2 (g) + H2O (l) + 2NH3 (g)`

Sodium carbonate is thermally stable upto a very high temperature. Therefore, this experiment can be utilised to distinguish between aqueous solutions of sodium carbonate and ammonium carbonate.

Heat both the test tubes containing abovementioned solutions and place a piece of moist red litmus paper at the mouth of both. The litmus paper which turns blue indicates the presence of ammonium carbonate in the corresponding test tube.

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