Q.Give the balanced equation for the reaction between chlorine with cold NaOH and hot NaOH.

Chlorine is prepared in the laboratory by oxidising a chloride (NaCl) or hydrochloric acid with MnO2/conc. H2SO4 (4NaCl + MnO2 + 4H2SO4 -> Cl2 + MnCl2 + 4NaHSO4 + 2H2O), or with KMnO4/K2Cr2O7, or from bleaching powder plus a mineral acid. Industrially it is manufactured either by electrolysis of brine (the chlor-alkali process — Cl2 at the anode, H2 plus NaOH at the cathode) or by Deacon's process, the catalytic (CuCl2) air-oxidation of HCl at ~723 K (4HCl + O2 -> 2H2O + 2Cl2), which gives a dilute chlorine mainly used for bleaching-powder manufacture.

Chlorine is a dense, greenish-yellow, toxic, pungent gas, soluble in water as "chlorine water." It is extremely reactive: it combines directly with almost every metal and non-metal to give chlorides, reacts explosively with hydrogen, strips hydrogen from hydrocarbons (turpentine -> carbon + HCl), and, in sunlight, slowly decomposes water to liberate oxygen. With ammonia it gives N2 (excess NH3) or explosive NCl3 (excess Cl2); with cold dilute alkali it disproportionates to chloride + hypochlorite, and with hot concentrated alkali to chloride + chlorate; it oxidises H2S to sulphur, Fe2+ to Fe3+, sulphite to sulphat …