Conditions necessary for rusting of iron:
(i) Iron is exposed to moist air.
(ii) Presence of water droplets in the atmosphere.
(iii) Presence of Oxygen.

(i) Rust is the formation of scaling reddish brown hydrated ferric oxide on the surface of iron containing materials.
(ii) This compound is known as rust and the phenomenon of formation of rust in known as rusting.
(iii) \( 4 \mathrm{Fe}+3 \mathrm{O}_{2}+\mathrm{xH}_{2} \mathrm{O} \rightarrow 2 \mathrm{Fe}_{2} \mathrm{O}_{3} \cdot \mathrm{xH}_{2} \mathrm{O}\\ \quad \quad \quad \quad \quad\quad\text { (Rust hydrated ferric oxide) } \) 

(i) A - reddish brown metal - Copper
(ii) When copper is heated at < 1370 K in the presence of oxygen, copper forms black colour Copper (II) oxide (CuO).
(iii) \(2 \mathrm{Cu}+\mathrm{O}_{2} \stackrel{\text { below } 1370 \mathrm{~K}}{\longrightarrow} \underset{\text { (copper (Il)oxide-black) }}{2 \mathrm{CuO}}\)
(iv) When copper is heated at >1370 K in the presence of oxygen, copper forms red colour Cop-per (I) oxide \((\mathrm{Cu}_{2} \mathrm{O} )\)
(v) \(4 \mathrm{Cu}+\mathrm{O}_{2} \stackrel{\text { above } 1370 \mathrm{~K}}{\longrightarrow} \underset{\text { (copper-I-oxide-red) }}{2 \mathrm{Cu_2O}}\)
(vi) A - copper (Cu)
(vii) B - copper (II) oxide (CuO) - Black coloured
(viii) \(\mathbf{C} - copper-I-oxide \left(\mathrm{Cu}_{2} \mathbf{O}\right)-\operatorname{Red}\) coloured

Smelting (in a Blast Furnace):
(i) The charge consisting of roasted ore, coke and limestone in the ratio 8:4:1 is smelted in a blast furnace by introducing it through the hopper arrangement at the top.
(ii) There are three important regions in the furnace.

a) The Lower Region (Combustion Zone):
(i) The temperature is at \(1500^{\circ} \mathrm{C}\).
(ii) In this region, coke burns with oxygen to form CO₂ when the charge comes in contact with a hot blast of air.
(iii) It is an exothermic reaction since heat is liberated.
\(\mathbf{C}+\mathbf{O}_{2} \underset{\Delta}{\stackrel{1500^{\circ} \mathrm{C}}{\longrightarrow}} \mathrm{CO}_{2}+ Heat\)
b) The Middle Region (Fusion Zone):
(i) The temperature prevails at \(1000^{\circ} \mathrm{C}\).
(ii) In this region, CO₂ is reduced to CO.
\(\mathrm{CO}_{2}+\mathrm{C} \underset{\Delta}{\stackrel{1000^{\circ} \mathrm{C}}{\longrightarrow}} 2 \mathrm{CO}-\text { Heat }\)
(iii) Limestone decomposes to calcium oxide and CO₂.
\(\mathrm{CaCO}_{3} \underset{\Delta}{\stackrel{1000^{\circ} \mathrm{C}}{\longrightarrow}} \mathrm{CaO}+CO_2-\text { Heat }\)
(iv) These two reactions are endothermic due to absorption of heat.
(v) Calcium oxide combines with silica to form calcium silicate slag.
\(\mathrm{CaO}+\mathrm{SiO}_{2} \longrightarrow \mathrm{CaSiO}_{3}\)
c) The Upper Region (Reduction Zone):
(i) The temperature prevails at \(\mathbf{4 0 0 ^ { \circ } \mathrm { C } \text { . }}\)
(ii) In this region carbon monoxide reduces ferric oxide to form a fairly pure spongy iron.
\(\mathrm{Fe}_{2} \mathrm{O}_{3}+3 \mathrm{CO} \stackrel{400^{\circ} \mathrm{C}}{\longrightarrow} 2 \mathrm{Fe}+3 \mathrm{CO}_{2}\uparrow\)
(iii) The molten iron is collected at the bottom of the furnace after removing the slag.
(iv) The iron thus formed is called pig iron.
(v) It is remelted and cast into different molds.
(vi) This iron is called cast iron.

a) Addition of caustic alkali to bauxite ore:
(i) Bauxite ore is finely ground and heated under pressure with a solution of concentrated caustic soda solution at 150^oC to obtain sodium meta aluminate.
(ii) Al₂O₃ + 2 NaOH → 2 NaAlO₂ + H₂O
(iii) On diluting sodium meta aluminate with water, a precipitate of aluminium hydroxide is formed.
(iv) NaAlO₂ + 2 H₂O → Al(OH)₃ + NaOH
(v) The precipitate is filtered, washed, dried and ignited at 1000^oC to get alumina.
(iv) \(2 \mathrm{Al}(\mathrm{OH})_{3} \stackrel{1000^{\circ} \mathrm{C}}{\longrightarrow} \mathrm{Al}_{2} \mathrm{O}_{3}+3 \mathrm{H}_{2} \mathrm{O}\)
b) (i) Electrolyte : Pure alumina + molten cryolite +fluorspar
(ii) Fluorspar is added to lowers the fusion temperature of electrolyte.

i) Metal A belongs to periods 3 and group 13 is Aluminium.
ii) When steam is passed over red hot aluminium, Aluminium oxide and Hydrogen is produced.
iii) when Aluminium react with strong caustic alkalis forming aluminates