CBSE Class 12 Chemistry Quiz | CBSE Class 12 Chemistry Multiple Choice Questions(MCQs) with Answers

Questions
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

Answer: 54 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

Answer: Na3PO4
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

Answer: Low T and high P
65 Identify the positively charged colloid.
A Haemoglobin
B Gold sol
C As2S3
D Clay

Answer: Haemoglobin
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

Answer: Galena
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

Answer: Argentite
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

Answer: roasting in O2
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

Answer: FeSiO3 and Cu2S
76 The composition of copper matte is
A Cu2S + FeS
B Cu2O + FeS
C Cu2S + Cu2O
D Cu2S + FeO

Answer: Cu2S + FeS
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

Answer: Al and Fe
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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