Q.1. Which one is malachite from the following? (2019)
Malachite : CuCO3.Cu(OH)2 (Green colour)
Q.2. The process of heating the concentrated ore in a limited supply of air or in the absence of air is known as: (2017)
In the process of metallurgy, Calcination is used for the concentration of ore to oxide. It is a process of heating an ore in a limited supply of air. If the ore is heated in the presence of excess of air then its ia known as roasting. Generally carbonate ores are calcined and hence carbon dioxide is given out.
Q.3. Extraction of gold and silver involes leaching with CN- ion. Silver is later recovered by :- (2017)
B: Zone refining
C: Displacement with Zn
Q.4. Match items of Column I with the items of Column II and assign the correct code : (2016)
(a) (b) (c) (d)
A: (iii) (iv) (v) (i)
B: (iv) (ii) (iii) (i)
C: (ii) (iii) (i) (v)
D: (i) (ii) (iii) (iv)
(iv) (ii) (iii) (i)
Cyanide process is used for extracting Au (gold) from low-grade ore by converting the Au to the water soluble coordination complex.
Froth flotation process is used for the dressing of sulphide ore such ZnS.
Electrolytic reduction is used for the extraction of Al. The extraction of aluminium is carried out in a steel tank lined inside with graphite. Here graphite used serves as a cathode.
Zone refining is used for ultra pure Ge element. An ingot of Ge is first purified by zone refining. Then a small amount of antimony is placed in the molten zone which is passed through the pure Ge with the proper choice of rate of heating and other variables.
Q.5. "Metals are usually not found as nitrates in their ores".
Out of the following two (a and b) reasons which is / are true for the above observation ?
(a) Metal nitrates are highly unstable
(b) Metal nitrates are highly soluble in water. (2015)
A: a is true but b is false
B: a and b are true
C: a and b are false
D: a is false but b is true
Metal nitrates are usually not found as nitrates in their ores because they are highly soluble in water.