Ores and Metallurgy MCQ Questions & Answers in Inorganic Chemistry | Chemistry
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161.
Which of the following condition favours the reduction of a metal oxide to metal ?
A
$$\Delta H = + ve,T\Delta S = + ve$$ at low temperature
B
$$\Delta H = + ve,T\Delta S = - ve$$ at any temperature
C
$$\Delta H = - ve,T\Delta S = - ve$$ at high temperature
D
$$\Delta H = - ve,T\Delta S = + ve$$ at any temperature
Answer :
$$\Delta H = - ve,T\Delta S = + ve$$ at any temperature
$$\Delta H = - ve,T\Delta S = + ve$$ at any temperature
162.
The reaction $$C{r_2}{O_3} + 2Al \to A{l_2}{O_3} + 2Cr$$ $$\left( {\Delta {G^ \circ } = - 421\,kJ} \right)$$ is thermodynamically feasible due to $$-ve$$ value of $$\Delta G.$$ Why does this reaction not take place at room temperature?
A
Certain amount of activation energy is essential for thermodynamically feasible reactions also.
B
Due to high melting point of chromium oxide the reaction does not take place.
C
Overall value of $$\Delta G$$ for the net reaction becomes positive.
D
Molecules of $$C{r_2}{O_3}$$ and $$Al$$ are not oriented properly.
Answer :
Certain amount of activation energy is essential for thermodynamically feasible reactions also.
The spontaneous reaction also requires a certain amount of activation energy therefore heating is required.
163.
Which one of the following ores is best concentrated by froth-flotation method?
A
Galena
B
Cassiterite
C
Magnetite
D
Malachite
Answer :
Magnetite
NOTE : Galena is $$PbS$$ and thus purified by froth floatation method. Froath floatation method is used to concentrate sulphide ores. This method is based on the preferential wetting properties with the froathing agent and water.
164.
Match the column I with column II and mark the appropriate choice.
Column I
Column II
a.
Metals used as semiconductors
1.
Aluminium
b.
Electrolytic reduction
2.
Zone refining
c.
Cyanide process
3.
Dressing of $$ZnS$$
d.
Froth floatation process
4.
Extraction of $$Ag$$
A
a - 1, b - 3, c - 2, d - 4
B
a - 3, b - 4, c - 2, d - 1
C
a - 4, b - 2, c - 3, d - 1
D
a - 2, b - 1, c - 4, d - 3
Answer :
a - 2, b - 1, c - 4, d - 3
No explanation is given for this question. Let's discuss the answer together.
165.
Chromatography is a useful method for purification of elements which are
A
very reactive
B
available in minute quantities
C
present in abundance
D
highly electropositive
Answer :
available in minute quantities
Chromatography is useful for purification of the elements which are available in minute quantities and the impurities are not very different in chemical properties from the element to be purified.
166.
The process of converting hydrated alumina into anhydrous alumina is called
A
roasting
B
smelting
C
dressing
D
calcination
Answer :
calcination
$$A{l_2}{O_3}.2{H_2}O \to A{l_2}{O_3} + 2{H_2}O$$ is calcination.
167.
Which of the following sulphides when heated strongly in air gives the corresponding metal without undergoing separate reduction of oxide?
A
$$C{u_2}S$$
B
$$FeS$$
C
$$HgS$$
D
$$ZnS$$
Answer :
$$HgS$$
When heated in air $$HgS$$ is converted into oxide which decomposes to give metal and oxygen.
$$\eqalign{
& 2HgS + 3{O_2} \to 2HgO + 2S{O_2} \cr
& 2HgO \to 2Hg + {O_2} \cr} $$
168.
During the process of electrolytic refining of copper, some metals present as impurity settle as ‘anode mud’. These are
A
$$Fe\,{\text{and}}\,Ni$$
B
$$Ag\,{\text{and}}\,Au$$
C
$$Pb\,{\text{and}}\,Zn$$
D
$$Sn\,{\text{and}}\,Ag$$
Answer :
$$Ag\,{\text{and}}\,Au$$
During the process of electrolytic refining $$Ag\,{\text{and}}\,Au$$ are obtained as anode mud.
169.
The name of the metal which is extracted from the ore is given below. Mark the example which is not correct.
A
Malachite - $$Cu$$
B
Calamine - $$Zn$$
C
Chromite - $$Cr$$
D
Dolomite - $$Al$$
Answer :
Dolomite - $$Al$$
Dolomite - $$CaC{O_3} \cdot MgC{O_3}$$
170.
If an impurity in a metal has a greater affinity for oxygen and is more easily oxidised than the metal, then the purification of metal may be carried out by