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Class 11
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Organic Chemistry Some Basic Principles and Techniques
why is nitric acid added to sodium extract before...

Question:
Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?

Answer:

While testing the Lassaigne's extract for the presence of halogens, it is first boiled with dilute nitric acid. This is done to decompose NaCN to HCN and Na₂S to H₂S and expel these gases. If any nitrogen and sulphur are present in the form of NaCN and Na₂S, then they are removed. The chemical equations involved in the reaction are represented as

NaCN + HNO₃ → NaNO₃ + HCN

Na₂S + 2HNO₃ → 2NaNO₃ + H₂S

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Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?

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Question:
Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?