Question 16.
Write the chemical equation for the following events.
a. Aluminum came in contact with air.
b. Iron filings are dropped in an aqueous solution of copper sulfate.
c. A reaction was brought about between ferric oxide and aluminum.
d. Electrolysis of alumina is done.
e. Zinc oxide is dissolved in dilute hydrochloric acid.
Answer:
(a) 4Al(s) + 3O2(l) → 2Al2O3(s)
The surface of the aluminum metal is covered with a thin layer of oxide that helps protect the metal from attack by air. So, normally, aluminum metal does not react with air. If the oxide layer is damaged, the aluminum metal is exposed to attack
(b) Iron is more electropositive than copper. It can displace Copper (Cu) from its salt Copper sulfate (CuSO4) and thus its colour changes from blue to green.
Fe + CuSO4 → FeSO4 + Cu
(c) The reaction of Ferric oxide and aluminum produces aluminum oxide and iron. The chemical equation is:
3Fe3O2 + 4Al → 2Al2O3 + 6Fe
(d) The electrode reactions are:
Anode reaction: 2O2- → O2 + 4e- (Oxidation)
Cathode reaction: Al3+→ Al (l)(Reduction)
(e) ZnO(aq)+2HCl(aq)→ZnCl2(aq)+H2O(l)
Zinc chloride and water are produced in the reaction.
