CBSE Class 12 Chemistry General Principles And Processes of Isolation of Elements Worksheet Set B

Answer: b

Question. Chromatographic method is based on the principle that
a) different components of a mixture are differently adsorbed on an adsorbent
b) same components of a mixture are differently adsorbed on an adsorbent
c) different components of a mixture are differently absorbed on an absorbent
d) None of the above

Answer: a

Question. If the sulphide ores of copper contains iron, then before heating, it is mixed with
a) silica
b) coke
c) carbon
d) coal

Answer: a

Question. Which of the following elements occurs in free state?
a) Iodine
b) Sulphur
c) Phosphorus
d) Magnesium

Answer: b

Question. Considering Ellingham diagram, which of the following metals can be used to reduce alumina?
a) Mg
b) Zn
c) Fe
d) Cu

Answer: a

Question. Which one of the following is a mineral of iron?
a) Malachite
b) Cassiterite
c) Pyrolusite
d) Magnetite

Answer: d

Question. An ore contains lead sulphide and zinc sulphide.
If froth floatation process is used, these can be separated
a) by using excess of pine oil
b) by using collection and froth stabilisers
c) by adjusting proportion of oil to water or using depressants
d) by using some suitable solvent in which either lead sulphide or zinc sulphide is soluble.

Answer: c

Question. In the extraction of copper from its sulphide ore, the metal finally obtained by the reduction of cuprous
oxide with
a) copper (I) sulphide (Cu₂S) 
b) sulphur dioxide (SO₂) 
c) iron sulphide (FeS)
d) carbon monoxide (CO)

Answer: a

Question. The ore which is concentrated by leaching process is
a) cuprite
b) argentite
c) sphalerite
d) haematite

Answer: b

Question. The froth stabilisers among the following are
a) pine oil
b) cresol
c) aniline
d) Both (b) and (c)

Answer: d

Question. Extraction of gold and silver involves leaching with CN⁻ ion. Silver is later recovered by
a) liquation
b) distillation
c) zone refining
d) displacement with Zn

Answer: d

Question. Which of the following elements is present as the impurity to the maximum extent in the pig iron?
a) Carbon
b) Silicon
c) Phosphorus
d) Manganese

Answer: a

Question. The Mond process is used for the
a) purification of Ni
b) extraction of Mo
c) purification of Zr & Ti
d) extraction of Zn

Answer: a

Question. Which of the following is not true in the context of roasting process?
a) The ore is heated in a regular supply of air
b) The sulphide ores of copper are heated in reverberatory furnace
c) 2ZnS + 3O₂ → 2ZnO+ 2SO₂ is a reaction that involves roasting process
d) Mg, Al and Zn oxides can be reduced by roasting process

Answer: d

Question. Sulphide ores are common for which of the following metals.
a) Ag, Cu and Pb
b) Ag, Cu and Sn
c) Ag, Mg and Pb
d) Al, Cu and Pb

Answer: a

Question. The ore that contains both iron and copper is
a) malachite
b) azurite
c) dolomite
d) copper pyrites

Answer: d

Question. Roasting of sulphides gives the gas X as a by-product. This is a colourless gas with choking smell of burnt sulphur and causes great damage to respiratory organs as a result of acid rain.
Its aqueous solution is acidic acts as a reducing agent and its acid has never been isolated.
The gas X is
a) H₂S 
b) SO₂
c) CO₂
d) SO₃

Answer: b

Question. Given, ΔG_f^° (CuO) = −129.7 kJ mol⁻¹,
                 ΔG_f^° (H₂O) = − 237.2  kJ mol⁻¹ and
                 ΔG_f^° (CO) = −137.2 kJ mol−1
The better reducing agent for the reduction of CuO is
a) H₂
b) CO
c) C
d) Any of these

Answer: a

Question. Froth floatation process for the concentration of ores is an illustration of the practical application of
a) absorption
b) adsorption
c) sedimentation
d) coagulation

Answer: b

Question. In the graph of Δ_rG° vs T for the formation of oxides,
a) Cu₂O  line is almost at the top
b) lines (C, CO) and (C, CO₂)  are at much higher positions in the graph
c) Both (a) and (b)
d) Neither (a) nor (b)

Answer: a

Question. The reducing agent used to reduce iron oxide in blast furnace is
a) silica
b) CO
c) C
d) lime

Answer: b

Question. Silica is added to the copper pyrites ore, when taken in reverberatory furnace for extraction of Cu.
This is because
a) it removes the impurity of iron oxide as slag
b) it reacts with Cu₂ O  to form slag
c) it reduces Cu₂ O  to Cu
d) it helps in separation of Cu from Fe

Answer: a

Question. Auto-reduction is not involved in the extraction of
a) copper
b) mercury
c) lead
d) aluminium

Answer: d

Question. In electrolytic refining method,
a) the impure metal is made to act as anode
b) a strip of the pure metal is used as cathode
c) anode and cathode are kept in a suitable electrolytic bath containing soluble salt of the same metal
d) All the above are true

Answer: d

Question. Stainless steel is rust proof because
a) an oxide layer of chromium protects it.
b) a stoichiometric compound is formed.
c) interstitial compound is formed between Cr and Fe.

Answer: b

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