1. (i) Ammonium chloride is a soluble salt prepared by ................ (precipitation, neutralisation).   2. (ii) When ammonium chloride is heated, it undergoes ................ (thermal decomposition, thermal dissociation).   3. (iii) Heating ammonium chloride with sodium hydroxide produces ................ (ammonia, nitrogen).   4. (iv) Heating a solution of ammonium chloride and sodium nitrite produces ................... (ammonia, nitrogen)