Chemistry
Explain the following:
(a) Zinc oxide can be reduced to zinc by using carbon monoxide, but aluminium oxide cannot be reduced by reducing a agent.
(b) During electrolysis of molten lead bromide, a graphite anode is preferred to other electrodes.
(c) Electrolysis of molten lead bromide is considered to be a redox reaction.
Answer
(a) Aluminium is placed above zinc in reactivity series. Hence, aluminium is more reactive than zinc and its oxide is stable and cannot be reduced by a reducing agent. Zinc being less reactive metal, its oxide is less stable and so it can be easily reduced by carbon monoxide.
(b) As graphite is unaffected by the reactive bromine vapours released at the anode hence, a graphite anode is preferred during the electrolysis of molten lead bromide
(c) Electrolysis of molten lead bromide involves oxidation and reduction reactions and hence is a redox reaction.
Reduction reaction at cathode:
Pb2+ + 2e- ⟶ Pb
Oxidation reaction at the anode:
Br1- - 1e2- ⟶ Br
Br + Br ⟶ Br2
Related Questions
With reference to the first three periods of the modern periodic table, answer the questions given below.
(a) What features of the atomic structure accounts for the similarities in the chemical properties of the elements in group VII A of the periodic table?
(b) Name the element which has the highest ionisation potential.
(c) What is the atomic number and name of the element present in 3rd period and 17th group of the periodic table?
The following questions are pertaining to various laboratory preparations
(a) Which property of hydrogen chloride is demonstrated by fountain experiment?
(b) Why hydrogen chloride gas is not collected over water?
(c) What is the source of nitrogen gas used in Haber's process?
4.2 grams of magnesium carbonate is decomposed by heating according to the question.
MgCO3 ⟶ MgO + CO2
Calculate the following
(a) Volume of carbon dioxide obtained at STP.
(b) Mass of MgO formed
[Atomic weight : Mg = 24, C = 12, O = 16]
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(b) Give the balanced chemical equation for the conversion of ammonia solution to an amphoteric hydroxide