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p-Block Elements – II — Chemistry STD 12 — Question

Tamilnadu BoardEnglish MediumSTD 12Chemistryp-Block Elements – II2 Marks
Question
Pure nitric acid is colourless, on standing it becomes yellow. Justify your answer.
✓

Answer

Nitric acid decomposes on exposure to sunlight or on being heated, into nitrogen dioxide, water and oxygen.
$
4 HNO _4 \rightarrow 4 NO _2+2 H _2 O + O _2
$
Due to this reaction pure acid or its concentrated solution becomes yellow on standing.

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