Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?
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Solution
The added nitric acid decomposes NaCN to HCN and Na2S to H2S. NaCN+HNO3→NaNO3+HCN Na2S+2HNO3→2HNO3+H2S This removes all the nitrogen and sulphur present. Hence, only halogen is available for testing.