This set of Extractive Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Extraction of Metals from Sulphide Ores”.
1. Lead is mostly used for which purpose?
a) Oxides
b) Batteries
c) Cables
d) Pipes
View Answer
Explanation: Lead has the most abundant use for the production of batteries. The reason for this is owing to good resistance given by lead against corrosion. It is also cheap compared to other metals which can be used for this purpose.
2. What is the chemical formula for Galena?
a) PbCO3
b) PbSO4
c) PbS
d) PbSO3
View Answer
Explanation: Galena is the most common ore of Lead. Its chemical formula is PbS. It is a sulphide mineral. It is associated with other sulphides like ZnS, FeS, CuS and other precious metals. Galena can be used as a semiconductor.
3. Why the temperature is not increased above 800°C during roasting of lead sulphide?
a) Galena tends to fuse
b) Instrument not available to go above 800°C temperature
c) Temperature is way above the melting point of lead
d) Sulphur content is reduced
View Answer
Explanation: Above 800°C, the vapour pressure of lead sulphide is very high. So, above this temperature, PbS tends to fuse. Noting the melting and boiling temperatures of lead, the roasting temperature is maintained around 700°C.
4. What is an important process before roasting in the extraction of lead?
a) Sintering
b) Concentration of ore
c) Slagging
d) Smelting
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Explanation: Before roasting, we have to concentrate the lead ore. Lead ore contains lead sulphide with other sulphides and some precious metals. So, the lead sulphide is separated from other sulphides and concentrated by the floatation method.
5. Galena fuses easily compared to other copper minerals.
a) True
b) False
View Answer
Explanation: Galena gets fused easily than copper minerals because of the low melting point of lead and also galena is brittle and can be easily broken into small pieces. This is also the reason why copper is not used as fuse wire.
6. Which machine is used for the roasting process of lead sulphide?
a) Blast furnace
b) Hydro cyclone
c) Reverberatory furnace
d) Dwight – Lloyd sintering machine
View Answer
Explanation: Dwight – Lloyd sintering machine is the best machine for roasting because it not only eliminates Sulphur from lead sulphide but also produces sinter for the smelting process. It reduces Sulphur to a very large extent which is about 1 – 2%.
7. Why an updraught sintering machine is preferred in the roasting process?
a) It is easier to install
b) Inexpensive machine
c) Rich SO2 production
d) Downdraught machines are all destroyed
View Answer
Explanation: Updraught sinter machines are preferred because they produce SO2 gas to a great extent. Also, it produces rich quality gas which can be used for the manufacture of acid. Downdraught sinter machines were used earlier and are still in use at some places.
8. Why the presence of iron after the roasting process of lead is of no use?
a) The atomic number of iron is less than lead
b) Lead and iron are immiscible
c) We do not get iron after the process
d) A mixture of iron and lead is very easy
View Answer
Explanation: Iron is needed after the roasting process for the formation of the matte. In the case of lead, the presence of iron is completely useless because iron and lead are completely immiscible. Iron sulphide gets oxidized during the roasting process and then gets reduced during the smelting process.
9. Complete the following roasting reaction:
PbS + O2 = ______ + SO2. (The reaction is not balanced)
a) PbO.SiO2
b) PbS
c) PbO.Si
d) PbO
View Answer
Explanation: The above-given reaction is a part of the roasting process for the extraction of lead. The reaction takes place in Dwight-Lloyd sintering machine. The reaction takes place below the fusion point. If the temperature is lower than sulphates may also form.
10. Why the bosh of the blast furnace water-cooled during the smelting process of lead oxide?
a) To obtain liquid metal
b) To ensure that the bosh temperature is low
c) Water is used as a lubricant
d) To reduce lead oxide
View Answer
Explanation: The bosh of the blast furnace is usually water-cooled to keep the temperature of the bosh low. It also ensures that the temperature of the outgoing gases is also low. This is important to reduce the loss of lead as vapour.
11. What is the importance of using atmospheric oxygen in the air blast?
a) To reduce coke consumption
b) To decrease the output rate
c) Atmospheric oxygen is cheaply available
d) Difficult to produce heat using coke
View Answer
Explanation: Atmospheric oxygen plays a very important role in the blast air. A small amount of atmospheric oxygen increases the output to a relatively large extent. It reduces the consumption of coke whose use is environmentally not good.
12. Scrap iron combines with silica in the blast furnace to increase the melting point of slag.
a) True
b) False
View Answer
Explanation: The purpose of using scrap iron in the charge is to reduce the melting point of slag. This is done when iron combines with silica to produce FeSiO3. Melting point is reduced to get liquid slag at the operating temperatures.
13. Which of the following specifies the importance of scrap iron used in a blast furnace?
a) It is used as a lubricant
b) It increases the lead losses in the slag
c) It decreases the lead losses in slag
d) It is used as a heat source
View Answer
Explanation: Scrap iron usage in the charge of a blast furnace is of very importance. One of which is it decreases the lead losses in the slag. It helps to recover lead from the slag. It also reduces the leftover PbS which was not roasted in the sintering machine. The recovery of lead from slag can be shown as:
PbSiO3 + Fe = FeSiO3 + Pb.
14. Which of the following is not a part of the layer of the products after the smelting process for the extraction of lead?
a) Slag
b) Base bullion
c) Lead
d) Sulphur dioxide gas
View Answer
Explanation: After the smelting process the product contains four layers which include slag, copper matte, speiss and lead. The gases such as Sulphur dioxide gas are released from the top of the blast furnace.
Sanfoundry Global Education & Learning Series – Extractive Metallurgy.
To practice all areas of Extractive Metallurgy, here is complete set of Multiple Choice Questions and Answers.
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