CBSE
Multiple Choice QuestionsAl2O3 can be converted to anhydrous AlCl3 by heating:
Al2O3 with HCl gas
Al2O3 with NaCl in solid state
a mixture of Al2O3 and carbon in dry Cl2 gas
a mixture of Al2O3 and carbon in dry Cl2 gas
Sulphide ores of metals are usually concentrated by froth flotation process. Which one of the following sulphide ores offers an exception and is concentrated by chemical leaching?
Argentite
Galena
Copper pyrite
Copper pyrite
Considering the Ellingham diagram, which of the following metals can be used to reduce alumina?
Fe
Zn
Cu
Mg
Which of the following statements, about the advantage of roasting of sulphide ore before reduction is not true?
Carbon and hydrogen are suitable reducing agent for metal sulphides
The ΔfGo of the sulphide is greater than those for CS2 and H2S
The ΔfGo is negative for roasting of sulphide ore to oxide
The ΔfGo is negative for roasting of sulphide ore to oxide
In cyanide extraction process of silver from argentite ore, the oxidising and reducing agents are respectively.
O2 and CO2
O2 and Zn dust
HNO3 and Zn dust
HNO3 and CO
Extraction of gold and silver involves leaching with CN– ion. Silver is later recovered by
Liquation
Distillation
Zone refining
Zone refining
The following reactions take place in the blast furnace in the preparation of impure iron. Identify the reaction pertaining to the formation of the slag.
Fe2O3 (s) + 3CO (g) → 2 Fe (l) +3CO2 (g)
CaCO3 (s) → CaO (s) + CO2 (g)
CaO (s) +SiO2 → CaSiO3 (s)
CaO (s) +SiO2 → CaSiO3 (s)
Copper sulphates dissolves in excess of KCN to give:
CuCN
[Cu(CN)4]3-
[Cu(CN)4]2-
[Cu(CN)4]2-
Extraction of gold and silver involves leaching with CN– ion. Silver is later recovered by
Liquation
Distillation
Zone refining
Zone refining
Which of the following statements in incorrect?
pure sodium metal dissolves in liquid ammonia to give blue solution
NaOH reacts with glass to give sodium silicate
Aluminium reacts with excess NaOH to give Al(OH)3
Aluminium reacts with excess NaOH to give Al(OH)3
