Why is nitric acid not used in the preparation of hydrogen ?
It is because nitric acid is a strong oxidising agent (because it decomposes to yield nascent oxygenas:
2HNO3⟶2NO2+H2O+[O]
and it oxidises the hydrogen formed to water.Only 1% dilute and cold nitric acid reacts with magnesium and manganese to liberate Hydrogen gas.
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