Question

Write chemical equation for the following events.
a. Aluminium came in contact with air.
b. Iron filings are dropped in aqueous solution of copper sulphate.
c. A reaction was brought about between ferric oxide and aluminium.
d. Electrolysis of alumina is done.
e. Zinc oxide is dissolved in dilute hydrochloric acid.

Answer 1

Write chemical equation for the following events.
a. Aluminium came in contact with air.
Aluminum is a very reactive metal. The outer surface of the metal is actually covered by a very thin layer of the oxide which keeps the metal protected from the air. But when the oxide layer is damaged, aluminum comes in contact with the air. It is easily attacked by air. Then aluminium starts reacting with the oxygen. It will burn as bright white flame to change into aluminum(III) oxide.
Chemical Equation:
$4Al+3O_2\to 2A{l}_2{O}_3$

b. Iron is more reactive than copper. It can displace Copper (Cu) from its salt Copper sulphate (CuSO₄) and its colour changes from blue to green.
Chemical Equation:
$Fe+CuS{O}_4\to FeS{O}_4+Cu$

c. Aluminium is more reactive than iron. Aluminium metal replaces iron from ferric oxide to form aluminium oxide and iron
Chemical Equation:
$2Al+F{e}_2{O}_3\to A{l}_2{O}_3+2Fe$

d.The electrolysis of alumina is carried out in a steel tank lined inside with graphite. The graphite lining serves as cathode. Anode is also made up of graphite rods hanging in the molten mass. The electrolyte consists of alumina dissolved in fused Cryolite(Na₃AlF₆) and Fluorspar(CaF₂). Cryolite lowers the melting point of alumina and fluorspar increases the fluidity of the mass so that the liberated aluminum metal may sink at the bottom of the cell. When electric current is passed through this mixture, the aluminum is collected at the cathode in molten state and sinks at the bottom.

Ionization of Alumina:2Al₂O₃ → 6O^-2 + 4Al⁺³
Reaction at Cathode: 4Al⁺³ + 12e^- → 4Al
Reaction at Anode: 6O^-2 → 3O₂ + 12e^-, C + O₂ → CO₂

e. Zinc Oxide is an inorganic compound with formula ZnO. It is insoluble in water. When Zinc oxide reacts with hydrochloric acid it forms zinc chloride and water. It also leads in the formation of small bubbles of hydrogen. This is double displacement reaction.
Chemical Equation:
$ZnO+HCl\to ZnC{l}_2+H_{2}O$