Physical and chemical properties of iron
Answer Text: Properties of iron:Physical properties:- It has a melting point of #420^oC# and a boiling point of #907^oC#;- Have a good thermal and electrical conductivity;- It is ductile and malleable;Chemical properties.(i). Reaction with air.- It readily rusts in presence of moist air hydrated brown iron (III) oxide; #Fe_2O_3 .H_2O(s)#Equation:#4Fe(s) + 2H_2O (l) + 3O_2 (g) to 2Fe_2O_3 .H_2O (l)#- When heated it reacts with oxygen to form tri-iron tetroxide; #Fe_3O_4#;Equation:#3Fe(s) + 2O_2 (g) to Fe_3O_4(s)#(ii). Reaction with water.- It does not readily react with cold water.- It however reacts with steam liberating hydrogen gas and forming tri-iron tetroxide.Equation:#3Fe(s) + 4_H_2O(g) to Fe_3O_4(s) + 4H_2(g)#(iii). Reaction withchlorine.- Hot iron glows in chlorine without further heating, forming black crystals of iron (III) chloride;- Iron (III) chloride sublimes on heating and will thus collect on the cooler parts of the apparatus;Equation:#2Fe(s) + 3Cl_2(g) to 2FeCl_3(s)#Note:- Iron (III) chloride fumes when it is exposed to damp (moist) air;Reason:- It is readily hydrolysed by water with evolution of hydrogen chloride gas;Equation:#FeCl_3(s) + 3H_2O(l) to Fe(OH)_3(s) + 3HCl(g)#(iv). Reaction with acids:-Hydrochloric acid:- Iron reacts with hydrochloric acid to liberate hydrogen gas.Equation:#2Fe(s) + HCl(aq) to FeCl_2(aq) + H_2(g)#-Sulphuric (VI) acid:#Fe(s) + H_2SO_4 (aq) to FeSO_4 (aq) + H_2 (g)#Note: With hot concentrated #H_2SO_4#;- The iron reduces hot concentrated #H_2SO_4# to sulphur (IV) oxide and it is itself oxidized to iron (III) sulphate.Equation:#2Fe(s) + 6H_2SO_4 (l) to Fe_2 (SO_4)_3(aq) + 6H_2O (l) + 3SO_2 (g)#-Nitric (V) acid.- Iron reacts with dilute nitric (V) acid to form nitrogen (IV) oxide and ammonia which then forms ammonium nitrate.Equation:#10HNO_3 (aq) + 4Fe(s) to 4Fe(NO_3)_2(aq) + NH_4NO_3(aq) + 3H_2O(l)#- Warm dilute nitric (V) acid gives iron (II) nitrate.- Concentrated nitric (V) cid renders the iron unreactive.Reason:- Formation of iron oxide as a protective layer on the metal surface.(vi). Reaction with sulphur.- Iron when heated in sulphur forms iron (II) sulphide.Equation:#Fe(s) + S(s) to FeS(s)#