Get premium membership and access revision papers with marking schemes, video lessons and live classes.

Processing. Please wait.

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 with
chlorine.
- 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)`