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Free download in PDF CBSE Class 12 Chemistry Multiple Choice Questions(MCQs) with Answers. Here Gkseries provide Chemistry Solve Questions and Answers for CBSE Class 12 Students.
61
3g of activated charcoal was added to 50 ml of acetic acid solution (0.06 M) in a flask. After an hour it was filtered and the strength of filtrate was found to be 0.042 M. The amount of acetic acid adsorbed per gram of charcoal is
[A]
42 mg
[B]
54 mg
[C]
36 mg
[D]
18 mg
62
During the adsorption of gas on the surface of solid, which of the following is true?
[A]
∆G < 0, ∆H > 0, ∆S < 0
[B]
∆G > 0, ∆H < 0, ∆S < 0
[C]
∆G < 0, ∆H < 0, ∆S < 0
[D]
∆G < 0, ∆H < 0, ∆S > 0
Answer: ∆G < 0, ∆H < 0, ∆S < 0
63
The best coagulant for the precipitation of Fe(OH)3 sol is
[A]
Na3PO4
[B]
Na2SO4
[C]
NaNO3
[D]
Na2HPO3
64
Which is favourable for physical adsorption?
[A]
Low T and high P
[B]
T and P do not affect
[C]
High T and high P
[D]
High T and low P
65
Identify the positively charged colloid.
[A]
Haemoglobin
[B]
Gold sol
[C]
As2S3
[D]
Clay
66
The stability of lyophobic sols is due to
[A]
the charge on particles
[B]
Tyndall effect.
[C]
adsorption of covalent molecules on the colloid
[D]
the size of the particles
Answer: the charge on particles
67
Gold sol can be prepared by
[A]
Reduction of AUCl3 with HCHO solution.
[B]
Peptization
[C]
Hydrolysis of AUCl3
[D]
Oxidation of Gold by aqua-regia
Answer: Reduction of AUCl3 with HCHO solution.
68
The term ‘sorption’ stands for ___________ .
[A]
adsorption
[B]
absorption
[C]
both absorption and adsorption
[D]
desorption
Answer: both absorption and adsorption
69
Extent of adsorption of adsorbate from solution phase increases with ___________ .
[A]
increase in amount of adsorbate in solution.
[B]
decrease in amount of adsorbate in solution.
[C]
decrease in surface area of adsorbent.
[D]
increase in temperature of solution.
Answer: increase in amount of adsorbate in solution.
70
Physical adsorption of a gaseous species may change to chemical adsorption with ___________ .
[A]
decrease in temperature
[B]
increase in temperature
[C]
increase in surface area of adsorbent
[D]
decrease in surface area of adsorbent
Answer: increase in temperature
71
Which of the following ore is best concentrated by froth floatation process?
[A]
Galena
[B]
Malachite
[C]
Magnetic
[D]
Siderite
72
Extraction of gold and silver involves leaching with CN–. Silver is later recovered by
[A]
Displacement by Zn
[B]
Liquation
[C]
Distillation
[D]
Zone refining
Answer: Displacement by Zn
73
Which one of the following ore is concentrated by chemical leaching method?
[A]
Argentite
[B]
Cinnabar
[C]
Copper pyrites
[D]
Galena
74
The first step in extraction of copper from CuFeS2 is
[A]
roasting in O2
[B]
magnetic separation
[C]
electrolysis of ore
[D]
reduction by carbon
75
Roasted copper pyrites on smelting with sand produces
[A]
FeSiO3 and Cu2S
[B]
Fe3(PO4)2 and Cu2S
[C]
CaSiO2 and Cu2O
[D]
Ca3(PO4)2 and Cu2S
76
The composition of copper matte is
[A]
Cu2S + FeS
[B]
Cu2O + FeS
[C]
Cu2S + Cu2O
[D]
Cu2S + FeO
77
A number of elements are available in earth’s crust but most abundant elements are ___________ .
[A]
Al and Fe
[B]
Cu and Ag
[C]
Al and Cu
[D]
Fe and Cu
78
In the extraction of chlorine by electrolysis of brine ___________ .
[A]
oxidation of Cl– ion to chlorine gas occurs.
[B]
reduction of Cl– ion to chlorine gas occurs.
[C]
For overall reaction ∆G° has negative value.
[D]
a displacement reaction takes place.
Answer: oxidation of Cl– ion to chlorine gas occurs.
79
Which of the following reactions is an example of auto reduction?
[A]
Fe3O4 + 4CO → 3Fe + 4CO2
[B]
Cu2O + C → 2Cu + CO
[C]
Cu2+ (aq) + Fe (s) → Cu (s) + Fe2+ (aq)
[D]
Cu20 + 1/2 Cu2S → 3Cu + 1/2 SO2
Answer: Cu20 + 1/2 Cu2S → 3Cu + 1/2 SO2
80
The electrolytic reduction technique is used in the extraction of
[A]
Highly electropostive elements.
[B]
Transition metals.
[C]
Highly electronegative elements.
[D]
Metalloids.
Answer: Highly electropostive elements.
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