Pure nitrogen is prepared in the laboratory by heating a mixture of

Options

A. `NH_(4)Cl+NaOH`
B. `NH_(4)NO_(3)+NaCl`
C. `NH_(4)Cl+NaNO_(2)`
D. `NH_(4)OH+NaCl`

Answer

C

Explanation

When an equimolar aqueous solution of ammonium chloride and sodium nitrite is heated, ammonium nitrite is first formed as a result of double decomposition reaction.
`NH_(4)Cl (aq)+NaNO_(2) (aq) rarr NH_(4)NO_(2) (aq)+NaCl (aq)`
It being unstable, decomposes immediately to form nitrogen gas.
`NH_(4)NO_(2)(aq) rarrN_(2)(g)+2H_(2)O(l)`
Small amounts of `NO` and `HNO_(3)` are also formed in this reaction. These impurities can be removed by passing the gas through aqueous sulphuric acid containing potassium dichromate.