一題會考PAST PAPER CHEM

When sodium nitrate is heated with the mixture of concentrated sulphuric acid and copper turnings, concentrated sulphuric acid firstly reacts with sodium nitrate to give nitric acid (which is dilute). The (dilute) nitric acid formed then reacts with copper turnings to give colourless nitrogen monoxide gas, which will then react with oxygen in air to give brown nitrogen dioxide gas.
NaNO3 + H2SO4 → HNO3 + NaHSO4
3Cu + 8HNO3 → 3Cu + 4H2O + 2NO
2NO + O2 → 2NO2

When sodium chloride is heated with the mixture of concentrated sulphuric acid and copper turnings, concentrated sulphuric acid firstly reacts with sodium nitrate to give colourless gas of hydrogen chloride gas, which does not react with copper turnings.

This may be out of the present HKCE syllabus.
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