Nitric Acid Study Guide PDF

Study of Compounds – Nitric Acid Nitric Acid Molecular formula: HNO3 Relative molecular mass: 63 Laboratory Preparation of Nitric Acid Reactions: KNO3 + H2SO4 KHSO4 + HNO3 NaNO3 + H2SO4 NaHSO4 + HNO3 Properties of Nitric Acid (A) Physical Properties  Pure acid (98% co...

Study of Compounds – Nitric Acid Nitric Acid Molecular formula: HNO3 Relative molecular mass: 63 Laboratory Preparation of Nitric Acid Reactions: KNO3 + H2SO4 KHSO4 + HNO3 NaNO3 + H2SO4 NaHSO4 + HNO3 Properties of Nitric Acid (A) Physical Properties  Pure acid (98% conc.) is colourless, suffocating and sour to taste.  It is heavier than water, with a specific gravity of 1.54.  Boiling point is 86°C, and freezing point is −42°C (B) Chemical Properties  Pure nitric acid is colourless, unstable and decomposes slightly even at room temperature and in the presence of sunlight. 4HNO3 → 4NO2 + 2H2O + O2  Nitric acid is a very strong monobasic acid and ionises almost completely in aqueous solution. HNO3 H+ + NO3−  Nitric acid neutralises alkalis to form salt and water. CaO + 2HNO3  Ca (NO3)2 + H2O CuO + 2HNO3  Cu (NO3)2 + H2O NaOH + HNO3  NaNO3 + H2O  Nitric acid reacts with carbonates and bicarbonates to produce salt, water and carbon dioxide. Na2CO3 + 2HNO3  2NaNO3 + H2O + CO2 NaHCO3 + HNO3  NaNO3 + H2O + CO2  Nitric acid oxidises carbon, sulphur and phosphorus to their highest oxides or oxy-acids such as carbon dioxide, sulphuric acid and phosphoric acid. C + 4HNO3  2H2O + 4NO2 + CO2 S + 6HNO3  H2SO4 + 2H2O + 6NO2 P4 + 20HNO3  4H3PO4 + 4H2O + 20NO2  Cold and dilute nitric acid oxidises metals to their nitrates and liberates nitric oxide. 3Cu + 8HNO3  Cu(NO3)2 + 2H2O + 2NO2 3Zn + 8HNO3  3Zn (NO3)2 + 4H2O + 2NO2  Concentrated nitric acid liberates nitrogen dioxide. Cu + 4HNO3  Cu(NO3)2 + 2H2O + 2NO2 Zn + 4HNO3  Zn (NO3)2 + 2H2O + 2NO2  Nitric acid (1 part by volume) mixed with conc. hydrochloric acid (3 parts by volume) produces a mixture called aqua regia. HNO3 + 3HCl  NOCl + 2H2O + 2[Cl] Aqua regia contains nascent chlorine and reacts with noble metals such as gold and platinum to produce chlorides. Pt + 4[Cl]  PtCl4 Au +3[Cl]  AuCl3 Uses of Nitric Acid  To etch designs on copper and brassware because it acts as a solvent for several metals except the noble metals.  To purify gold with impurities of Cu, Ag and Zn which dissolve in nitric acid.  It acts as a rocket fuel oxidant.  In preparation of fertilisers such as Ca(NO3)2 and NH4NO3.  In the preparation of aqua regia, which dissolves noble metals.