Pb and Sn are extracted from their chief ore by:
1. carbon reduction and self-reduction respectively.
2. self-reduction and carbon reduction respectively.
3. electrolysis and self-reduction respectively.
4. self-reduction and self-reduction respectively.
Which of the following statements is incorrect?
(1) Cassiterite ore of tin contains the impurities of Wol-framite which are separated by electromagnetic separator.
(2) Tin metal is obtained by the carbon reduction of black tin.
(3) In the extraction of lead from galena, the roasting and self-reduction are carried in the same furnace at different temperatures.
(4) Reducing agent of haematite in blast-furnace is coke in upper part and CO in lower part of furnace.
Which of the following process is used in the extractive metallurgy of magnesium?
1. Fused salt electrolysis
2. Self reduction
3. Aqueous solution electrolysis
4. Thermite process.
White bauxite is purified by:
(1) Baeyer's process
(2) Hoop's process
(3) Serpeck's process
(4) Hall's process
Which of the following statements is correct?
(1) In Hall-heroult process, the electrolyte used is a molten mixture of alumina, sodium hydroxide and cryolite.
(2) Lead is extracted from its chief ore by both carbon reduction and self reduction.
(3) Tin is extracted from its chief ore by carbon monoxide reduction.
(4) Siderite, cassiterite and argentite are carbonate ores.
Match column (I) with column (II) and select the correct answer using codes given below in the lists.
Column - I Column - II
(i) Cynide process (a) Extraction of Al
(ii) Self reduction (b) Extraction of Ag
(iii) Electrolytic reduction (c) Extraction of Cu
(iv) Carbon reduction (d) Extraction of Sn
(1) (i)-(b), (ii)-(c), (iii)-(a), (iv)-(d)
(2) (i)-(b), (ii)-(d), (iii)-(a), (iv)-(c)
(3) (i)-(d), (ii)-(a), (iii)-(c), (iv)-(b)
(4) (i)-(c), (ii)-(b), (iii)-(d), (iv)-(a)
Assertion : The reduction of a metal oxide is easier if the metal formed is in liquid state
at the temperature of reduction.
Reason : The value of entropy change +S of the reduction process is more on +ve side when the metal formed is in liquid state and the metal oxide being reduced is in solid state. Thus the value of becomes more on negative side.
Assertion : Extraction of gold from its native ore involves leaching the metal with dilute
solution of NaCN in presence of air.
Reason : This is an oxidation reaction and leads to the formation of a soluble complex.
Assertion : Silica is added as a flux in reverberatory furnace, in the extraction of copper from copper pyrites.
Reason : Silica decreases the melting point of the ore and remove the impurity of lead sulphide as
Assertion : Cast iron is different from pig iron.
Reason : Cast iron is made by melting pig iron with scrap iron and coke using hot air blast and has about 3% carbon content.