Question

Metal ‘A’ is used in the thermite process as a reducing agent. When ‘A’ is heated with oxygen it gives an oxide ‘B’ which is amphoteric in nature. Identify A and B. Illustrate with the help of chemical equations the reaction of B with HCl and NaOH respectively.

          OR

a) “Carbon cannot be used to reduce metal oxides of sodium, magnesium, calcium, and aluminium to respective metals”. Comment.

b) These metals are obtained by electrolytic reduction of their molten chloride. Write the reactions that occur at the anode and cathode during the electrolytic reduction of molten sodium chloride.

c) Illustrate with the help of a chemical equation reduction of manganese dioxide with Aluminium powder.

Answer 1

(A) - Aluminium ) (B) - Al₂O₃ 

Al₂O₃ + 6HCl —-----> 2AlCl₃ + 3H₂O 

Al₂O₃ + 2NaOH —-----> 2NaAlO₂ + H₂O 

    OR 

(a) Carbon cannot reduce the oxides of sodium, magnesium, calcium, aluminium, etc., to the respective metals. This is because these metals have more affinity for oxygen than carbon. (Metals, Na, Mg, Ca and Al have more affinity towards oxygen than C) 

(b) The reactions are 

– At cathode 

Na⁺+ e^– → Na 

– At anode 

2Cl^– → Cl₂ + 2e^– 

(c) 3MnO₂ (s) + 4Al(s) → 3Mn(l) + 2Al₂O₃ (s) + Heat