Nitrogen and its inorganic compounds

I Introduction Nitrogen is a chemical with symbol N and atomic number The standard atomic weight of Nitrogen is 14 At room temperature, it is a transparent, odorless diatomic gas Nitrogen forms about 80% of Earth’s atmosphere and is the most abundant uncombined element Many industrially important compounds such as: ammonia, nitric acid, propellant, explosives, cyanides and some types of fertilizers contain nitrogen Moreover, Nitrogen is a nonmetal, its electronegativity is 3.04 It is unreactive at standard temperature and pressure At atmospheric pressure, molecular nitrogen liquefies and freezes at -210oC Below -237.6oC, nitrogen assumes the cubic crystal allotropic form (called the alpha phase) Liquid nitrogen, a fluid resembling water in appearance, but with 80.8% of the density (the density of liquid nitrogen at its boiling point is 0.808g/ml), is a common cryogen II Nitrogen’s properties In general, nitrogen is un-reactive at standard temperature and pressure because of strong triple bond Reaction with H2: N2 +H2 ⇄ NH3↑ (100oC, high pressure, catalyst: Fe) Reactions with O2 N2 + O2 → NO↑ (>2000oC) N2 +O2→NO2↑ Metal burns in nitrogen N2 + Al → 2AlN (Aluminium nitride) N2 +3 Mg → Mg3N2 (Magnesium nitride) Metal nitrides are hydrolyzed by water Mg3N2+ H2O → 3Mg(OH)2+2NH3↑ III Produce nitrogen (N2) Industry: produced by fractional distillation of liquid air Laboratory a) Decay some ammonium salts (NH4+) by heat NH4NO2 → N2↑ + H2O ( to) NH4Cr2O7 → N2↑ + Cr2O3 + 4H2O ( to) NH4NO3 → N2↑ + 1/2O2↑ + 2H2O b) 2NH3 + 3O2 → N2↑ + 6H2O (900oC) 2NH3 + 3CuO → N2 + 3Cu + 3H2O (to) c) Treat an aqueous solution of ammonium chloride(NH4Cl) with sodium nitrite (NaNO2): NH4Cl + NaNO2 → N2↑ + NaCl + H2O IV Uses of N2 +) Nitrogen is used to produce ammonia and nitrates are key industrial fertilizers +) Nutrients for all plants have this element +)The main use of liquid nitrogen is a refrigerant A Ammonia (NH3) and ammonium salts (NH4+) A.1 Ammonia (NH3) I Ammonia is a colorless gas with a characteristic pungent smell II Properties The ammonia molecule has a lone pair electron air, which makes ammonia a base, a proton acceptor NH3 + H2O ⇄ NH4+ + OH2 NH3’ reactions with acid: NH3 + HCl → NH4Cl 2NH3 + H2SO4 → (NH4)2SO4 NH3 + HNO3 → NH4NO3 NH3’s reactions with metal cations: Ag+ + 2NH3 → [Ag(NH3)2]+ Cu2+ + 4NH3 → [Cu(NH3)4]2+ Zn2+ + 4NH3 → [Zn(NH3)4]2+ Produce Urea ((NH)2CO): 2NH3+ CO2→ H2N─COONH4 H2N─COONH4 → (NH2)2CO (dehydration) NH3’s displacement reactions: displace 1, 2, or H atom by alkali metals Na + NH3 → NaNH2 + ½ H2↑ (mole fraction: 1:1) 2Na + NH3 → Na2NH + H2↑ (mole fraction: 2:1) 3Na + NH3 → Na3N + 3/2H2↑ (mole fraction: 3:1) Ammonia’s reactions with metal: 2NH3 + 2Al → 2AlN + 3H2↑ (to) Reduction reactions: N2 + H2 NH3↑ (.100oC,high pressure , catalyst: Fe) 2NH3 + 3O2 → N2↑ + 6H2O (900oC) 4NH3 + 5O2 → 4NO↑ + 6H2O (250oC, catalyst: Pt) 2NH3 + 3Cl2 → N2↑ + 6HCl 2NH3 + 3CuO → N2↑ + 3Cu↓ + 3H2O (to) III Produce ammonia Industry: N2 +H2 ⇄ NH3↑ (100oC, high pressure, catalyst: Fe) Laboratory a) Treat an aqueous solution of ammonium salts with alkali liquid NH4Cl + NaOH → NaCl + NH3↑ + H2O b) Hydrolyze sodium nitride: Ca3N2 + 6H2O → 3Ca(OH)2 +2 NH3 AlN +3H2O → Al(OH)3↓ + NH3↑ IV.Uses +) Ammonia is mostly used to produce acid nitric acid, fertilizers +) People use ammonia to produce hydrazine (N2H4) +)Solution of NH3 in water is used as a general purpose cleaner for many surfaces A.2 Ammonium salts (NH4+) I Ammonium salts are soluble in water (NH4+) is hydrolyzed in water II Properties Double displacement reactions: (NH4)2SO4 + Ba(OH)2 → BaSO4↓ + 2NH3↑ + 2H2O (NH4)2SO3 + 2HCl → 2NH4Cl + SO2↑ + H2O NH4Cl + AgNO3 → AgCl↓+ NH4NO3 Decay ammonium salts by heat NH4Cl → NH3↑ + Cl2↑ ( to) (NH4)2SO4 → 2NH3↑ + H2SO4 ( to) (NH4)2CO3 → NH3↑ + NH4HCO3 (to) NH4HCO3 → NH3↑ + CO2↑ + H2O (Sodium bicarbonate, referred to as ‘baking soda’, is primarily used in baking) III Produce ammonium salts Treat NH3 with acid liquids NH3 + HNO3 → NH4NO3 NH3 + H2SO4 → (NH4)2SO4 IV Uses +) Ammonium salts are used to produce fertilizers, explosives and sodium bicarbonate (NH4HCO3) +) Ammonium salts are also used to clean metal surfaces B Nitric acid (HNO3) I Nitric acid has a coordinate covalent bond Oxidation number nitrogen element in nitric acid is +5 Nitric acid is subject to light decomposition and it’s decayed: 4HNO3 → 4NO2↑ + O2↑ + 2H2O The nitrogen dioxide (NO2) remains dissolved in the nitric acid coloring it yellow II Properties Acidity Nitric acid is a strong acid: HNO3 + H2O → H3O+ + NO3Reactions with bases, base anhydrides, salts produce nitrate salts HNO3 + Fe(OH)3 → Fe(NO3)3 + 3H2O 2HNO3 + CuO → Cu(NO3)2 + H2O 2HNO3 + Na2CO3 → NaNO3 + CO2↑ + H2O HNO3 is a strong oxidizing agent because the nitrogen’s oxidation number is +5 Reactions of nitric acid with almost metals (except gold and platinum) produce metal nitrate salts (M(NO3)n) (n is the highest valence of that metal) and reducing products of HNO3 (such as NO, NO2, N2O, N2, NH3 or NH4NO3), depend on nitric acid’s concentration and metal’s reduction) Fe + 6HNO3 concentrated → Fe(NO3)3 + 3NO2↑ + 3H2O ( to) 3Cu + 8HNO3 dilute → 3Cu(NO3)2 + 2NO↑ + H2O 8Al + 30HNO3 dilute → 8Al(NO3)3+ 3N2O↑+ 15H2O 4Zn+ 10HNO3 very dilute →4Zn(NO3)2+ NH4NO3+ 3H2O Reactions with some nonmetals such as: S, P, C,… produce acidic oxide with highest oxidation number S +6HNO3 → H2SO4 + 6NO2↑ + 2H2O 3P + 5HNO3 +2H2O → 3H3PO4 + 5NO↑ C + 4HNO3 → CO2↑ + 4NO2↑ + 2H2O III.Produce HNO3 Industry: 4NH3 + 5O2 → 4NO↑ + 6H2O ( to) NO + O2 → NO2 3NO2 + H2O → 2HNO3 + NO↑ OR: 4NO2 + O2 + 2H2O → 4HNO3 Laboratory H2SO4 concentrated + KNO3 → KHSO4 + HNO3 (ĐK PƯ: to) IV Uses Nitric acid is mainly for the use of producing TNT, dyes, pharmaceutical products, ect… C Nitrate salts (NO3-) Every nitrate salt is soluble in water and The color of this liquid depends on cation Mn+ because ion NO3- is colorless I Properties of ion NO31 In acidic environment, ion NO3- has the oxidation like nitric acid 3Cu0 + 8H+ + NO3- → 3Cu2+ + 2NO↑ + 4H2O In alkaline environment, ion NO3- is reduced by Be, Zn, Al and NH3 is the reducing product 4Zn + KNO3 + 7KOH → 4K2ZnO2 + NH3↑ + 2H2O 8Al + 3NaNO3 + 5NaOH + 2H2O → 8NaAlO2 + 3NH3 ↑ Decay nitrate salts by heat a) Strong metals (K, Na, Ba, Ca) M(NO3)n → M(NO2)n + n/2O2↑ (to) b) Medium metals ((Mg, Al, Mn, Zn, Cr, Fe, Ni, Sn, Pb, Cu) 2M(NO3)n → M2On + n/2O2↑ + 2nNO2↑ c) Weak metals (Hg, Ag, Pt, Au) 2M(NO3)n → 2M↓ + n/2O2↑ + 2nNO2↑ II Uses +) Nitrate salts are mainly for the use of producing fertilizers such as: (NH4)2SO4, NH4NO3, (NH2)2CO +) Potassium nitrate (KNO3) is used to produce gunpowder (contain 75% KNO3, 10% S 15% C) 2KNO3 + 3C + S → K2S + N2↑ + 3CO2↑