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P-Block - Class 12 MCQ

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30 Questions MCQ Test - P-Block

P-Block for Class 12 2024 is part of Class 12 preparation. The P-Block questions and answers have been prepared according to the Class 12 exam syllabus.The P-Block MCQs are made for Class 12 2024 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for P-Block below.

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P-Block - Question 1

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Borax on heating with cobalt oxide forms a blue bead of :

A.
Co(BO₂)₂
B.
CoBO₂
C.
Co₃(BO₃)₂
D.
Na₃Co(BO₃)₂

Detailed Solution for P-Block - Question 1

Na₂B₄O₇ → 2NaBO₂ + B₂O₃
B₂O₃ + Co → CoO + B₂O₃ or Co(BO₂)₂
(Blue bead)

P-Block - Question 2

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On adding ammonium hydroxide solution to AI₂(SO₄)₃ (aq):

A.
a precipitate is formed which does not dissolve in excess of ammonium hydroxide
B.
a precipotate is formed which dissolves in excess of ammonia solution
C.
no precipitate is formed
D.
none of the above

Detailed Solution for P-Block - Question 2

Al₂(SO₄)₃ + 6NH₄OH → 2AI (OH)₃ + 3(NH₄)₂ SO₄
AI(OH)₃ is insoluble in NH₄OH
but soluble in NaOH

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P-Block - Question 3

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Aluminium becomes passive in nitric acid because it:

A.
is a noble metal
B.
forms a thin film of oxide
C.
positive reduction potential
D.
none of the above

Detailed Solution for P-Block - Question 3

Surface of AI forms AI₂O₃ in nitric acid and becomes passive.

P-Block - Question 4

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AI and Ga have the same covalent radii because of :

A.
greater shielding power of s-electrons of Ga atoms
B.
poor shielding power of s-electrons of Ga atoms
C.
poor shielding power of d-electrons of Ga atoms
D.
greater shielding power of d-electrons of Ga atoms

Detailed Solution for P-Block - Question 4

It is a reason for given fact.

P-Block - Question 5

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Corundum is:

A.
SiO₂
B.
AI₂O₃
C.
CaF₂
D.
Cr₂O₃

Detailed Solution for P-Block - Question 5

It is a fact

P-Block - Question 6

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Aqueous solution of potash alum is:

A.
alkaline
B.
acidic
C.
neutral
D.
none of these

Detailed Solution for P-Block - Question 6

Due to hydrolysis of AI³⁺ ions

P-Block - Question 7

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Hybridisation of boron in diborane is :

A.
sp
B.
sp²
C.
sp³
D.
sp³d²

Detailed Solution for P-Block - Question 7

sp^3-hybridisation, but four bonds are neither linear nor in one plane.

P-Block - Question 8

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BCI₃ does not exist as dimer but BH₃exist as dimer (B₂H₆) because:

A.
chlorine is more electronegative than hydrogen
B.
there is pπ-pπ back bonding in BCI₃ but BH₃ does not contain such multiple bonding
C.
Large-sized chlorine atoms do not fit in between the small boron atoms, whereas small-sized hydrogen atoms fit between boron atoms
D.
none of the above

P-Block - Question 9

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Aluminum is more reactive than iron, but aluminium is less easily corroded than iron because:

A.
aluminium is a noble metal
B.
oxygen forms a protective oxide layer
C.
iron undergoes reaction easily with water
D.
iron forms both mono and divalent ions

Detailed Solution for P-Block - Question 9

The formation of oxide film on AI surface prevents it from further corrosion.

P-Block - Question 10

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The cryolite is:

A.
NaAIO₃
B.
Na₃AIF₆
C.
Na₃AIO₃
D.
Na₂AIF₅

Detailed Solution for P-Block - Question 10

Crysolite (Na₃AIF₆) is added to AI₂O₃ before electrolysis tp lower the fusion temperature of bauxite in order to dissolve it and making good conductor of current.

P-Block - Question 11

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Which of the following is pseudoalum?

A.
(NH₄)₂SO₄.Fe₂(SO₄)₃.24H₂O
B.
K₂SO₄.AI₂(SO₄)₃.24H₂O
C.
MnSO₄.AI₂(SO₄)₃.24H₂O
D.
none of the above

Detailed Solution for P-Block - Question 11

General formula of alum is
M₂SO₄.M₂(SO₄)₃.24H₂O

P-Block - Question 12

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Nickeloy is an alloy containing.

A.
Ni+Cu+Cr
B.
AI+Cu+Cr
C.
Ni+AI+Cu
D.
none of these

Detailed Solution for P-Block - Question 12

The alloy of Ni+AI+Cu is called nickeloy.

P-Block - Question 13

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Aqueous ammonia is used as a precipitating reagent for AI³⁺ ions as AI(OH)₃ rather than aqueous NaOH, because:

A.
NH₊⁴ is a weak base
B.
NaOH is a very strong base
C.
NaOH forms [AI(OH)₄]^- ions
D.
NaOH forms [AI(OH)₂]⁺ ions

Detailed Solution for P-Block - Question 13

AlCl₃ + 3NaOH → Al(OH)₃ + 3NaCl
Al(OH)₃+ OH^- → Al(OH)^-₄(soluble)

P-Block - Question 14

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Borazole is obtained by reaction of :

A.
NH₃+B₂H₆ in 2:1 ratio
B.
NH₃+B₂H₆ in 1:2 ratio
C.
NH₃+B₂H₆ in 1:4 ratio
D.
NH₃+B₂H₆ in 4:1 ratio

Detailed Solution for P-Block - Question 14

P-Block - Question 15

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B-F bond order in BF₃ is:

A.
1
B.
2
C.
3
D.
4/3

Detailed Solution for P-Block - Question 15

Due to back bonding (pπ-pπ) giving resonance, bond order in BF₃ is 1.33

P-Block - Question 16

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Boric acid on heating at 150⁰C gives:

A.
B₂O₃
B.
H₂B₄O₇
C.
HBO₂
D.
H₂BO₃

Detailed Solution for P-Block - Question 16

P-Block - Question 17

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In AI₂CI₆, which statement is incorrect?

A.
Four AI-CI bond are same of length and two of different length
B.
Six AI-CI bond are of same of length and two of different length
C.
The angle CI-AI-CI is 110⁰ and 93⁰
D.
The angle AI-CI-AI is 87⁰

Detailed Solution for P-Block - Question 17

AI₂CI₆ has the structure given below:

Bond distance between Al—CI bond forming bridge is 2-21 Aº whereas all other AI—CI bonds have bond lengths 2-06 A.
Angles Cl—Al-—-Cl are 110° and 93° and Al—CI—Al bond is 87°

P-Block - Question 18

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The stability of +1 oxidation state among AI,Ga,In and TI increases in the sequence:

A.
Ga < In < AI < TI
B.
AI < Ga < In < TI
C.
TI < In < Ga < AI
D.
In < TI < Ga < AI

Detailed Solution for P-Block - Question 18

This is +1 oxidation state stability order due to inert pair effect.

P-Block - Question 19

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Boric acid is an acid because its molecule:
H₃BO₃ is monobasic Lewis acid and accept OH^- from H₂O forming one proton or H⁺.

A.
combines with proton from water molecule
B.
contains replaceable H⁺ ion
C.
given up a proton
D.
accepts OH^- from water releasing proton

Detailed Solution for P-Block - Question 19

H₃BO₃+H₂O → B(OH)^-₄ + H⁺

P-Block - Question 20

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Which of the following has the minimum heat of dissociation?

A.
[(CH₃)₃ N → BF₃]
B.
[(CH₃)₃ N → B(CH₃)F₂]
C.
[(CH₃)₃ N → B(CH₃)₂F]
D.
[(CH₃)₃ N → B(CH₃)₃]

Detailed Solution for P-Block - Question 20

The tendency of trimethyl boron to act as Lewis acid decreases due to +I effect of CH₃ gp. and thus, coordination becomes weaker.

P-Block - Question 21

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Aluminium chloride exists as dimer,AI₂CI₆ in soild state as well as in solution of non-polar solvent such as benzene. When dissolved in water it gives:

A.
AI₂O₃ + 6HCI
B.
[AI(H₂O)₆]³⁺ + 3CI^-
C.
[AI(OH)₆]^3-+3HCI
D.
AI³⁺ + 3CI^-

Detailed Solution for P-Block - Question 21

AICI₃ is hydrated in water and behaves as ionic compound

P-Block - Question 22

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The state of hybridisation of boron and oxygen atoms in boric acid (H₃BO₃) are respectively:

A.
sp³ and sp³
B.
sp² and sp³
C.
sp³ and sp²
D.
sp² and sp²

Detailed Solution for P-Block - Question 22

In H₃BO₃, B is sp²-hybridized and oxygen is sp³-hybridized having two lone pair on it.

P-Block - Question 23

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Graphite is good conductor of current but diamond is non-conductor because:

A.
diamond is hard and graphite is soft
B.
graphite and diamond have different atomic configuration
C.
graphite is composed of positively
D.
graphite has hexagonal layer structure with mobile p-electrons -charged carbon ions while diamond has continuous tetrahedral covalent structure with no free electrons

Detailed Solution for P-Block - Question 23

It is the reason for given fact

P-Block - Question 24

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Carbon dioxide is a gas but silica is a solid because:

A.
carbon dioxide is composed of discrete covalent CO₂ molecules whereas silica has continuous tetrahedral structure.
B.
CO₂ molecules are lighter than SiO₂ molecules
C.
CO₂ is more acidic than SiO₂
D.
melting point of silica is very high

Detailed Solution for P-Block - Question 24

It is the reason for given fact

P-Block - Question 25

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Which is not correct?

A.
Ge(OH)₂ is amphoteric
B.
GeCI₂is more stable than GeCI₄
C.
GeO₂is weakly acidic
D.
In HCI, [GeCI₄]^2-ion is formed from GeCI₂

Detailed Solution for P-Block - Question 25

Ge possesses more tedency to show +4 oxidation state.

P-Block - Question 26

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Aluminium carbide reacts with dil. HCI to give:

A.
C₂H₂
B.
C₂H₆
C.
CH₄
D.
C₂H₆

Detailed Solution for P-Block - Question 26

P-Block - Question 27

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Mg₂C₃ has the following characteristics:

A.
It is called magnesium allyide
B.
It conatins Mg2+ and ions
C.
It on hyrolysis gives propyne
D.
all of the above

Detailed Solution for P-Block - Question 27

P-Block - Question 28

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White lead or basic lead carbonate is:

A.
Pb(OH)₂.2PbCO₃
B.
Pb(OH)₂.Pb(CH₃COO)₂
C.
PbCO₃
D.
PbCO₃.Pb(OH)₂

Detailed Solution for P-Block - Question 28

It is a fact; also known as white lead.

P-Block - Question 29

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R₃SiCI on hydrolysis forms:

A.
R₃SiOH
B.
R₃Si-O-SiR₃
C.
R₂Si=O
D.
none of these

Detailed Solution for P-Block - Question 29

P-Block - Question 30

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Pyrosilicate ion is:

A.
SiO^2-₃
B.
SiO^4-₄
C.
Si₂O^6-₇
D.
Si₂O^2-₅

Detailed Solution for P-Block - Question 30

it is a fact

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P-Block MCQs with Answers

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