Nitrogen and its Compounds: Laboratory preparation of nitrogen gas from ammonium nitrite (NH₄NO₂)

4.0 Nitrogen and its Compounds

4.2.2 Laboratory preparation of nitrogen gas from ammonium nitrite (NH₄NO₂)

Figure 4.2: Set-up to prepare nitrogen gas in the laboratory

NB: Ammonium nitrite (NH₄NO₂) is unstable; so it is freshly prepared first, by reacting ammonium chloride (NH₄Cl) with sodium nitrite (NaNO₂). Then ammonium nitrite thermally decomposes to produce nitrogen gas and steam.

Questions 4.2.2

1. Write an equation for the reaction between ammonium chloride and sodium nitrite to produce ammonium nitrite.
2. Write an equation for the thermal decomposition of ammonium nitrite to produce nitrogen gas and steam.
3. State the physical properties of nitrogen in terms of solubility in water, color, and density compared to that of air (N = 14; O = 16). What, in real leaf, is an indication that nitrogen gas has no smell?
4. Explain how you would modify (change) the set-up to obtain dry nitrogen gas.
5. In terms of bonding within its molecules, explain why nitrogen is largely unreactive.
6. Explain why burning magnesium reacts with nitrogen even though the latter is largely unreactive. Write an equation for the reaction.
7. In an experiment to prepare nitrogen gas, 3.45 g of sodium nitrite was reacted with ammonium chloride to produce ammonium nitrite first. Determine the
   1. mass of ammonium chloride that was required to react completely with sodium nitrite
   2. mass of ammonium nitrite produced in the reaction
   3. mass of nitrogen gas produced by thermally decomposing the ammonium nitrite.
   4. volume at room temperature and pressure (r.t.p) of nitrogen gas produced in the reaction
      (Na = 23; Cl = 35.5; N = 14; O = 16; H = 1; molar gas volume at r.t.p = 24 dm³).
8. Nitrogen is unreactive but makes up 78% of the air. It dilutes oxygen which supports burning. Suggest a reason why the dilution is important.

NB: Nitrogen gas is unique. It gives negative results with all tests. It is colourless, odourless, insoluble, does not burn, does not support burning, has no affect on wet litmus paper and so on.