Question Set C

TN 12th Standard Chemistry p - Block Elements - I Previous Year Question Papers Study Material - QB365

Download Tamil Nadu 12th Standard Chemistry question papers, model tests, one-mark questions, important questions, and public exam papers in PDF format. Free study materials and answer keys for TN State Board students.

Questions:

Multiple Choice Question

50 x 1 = 50

Packing fraction of a simple cubic arrangement is _______.

(a)

68%

(b)

74%

(c)

52.38%

(d)

83%

The compound that reacts faster with Lucas reagent is ________.

(a)

butan-l-ol

(b)

butan-2-ol

(c)

2-methyl propan-1-ol

(d)

2-methyl propan-2-ol

Which one of the following is most basic?

(a)

2,4 – dichloroaniline

(b)

2,4 – dimethyl aniline

(c)

2,4 – dinitroaniline

(d)

2,4 – dibromoaniline

Secondary nitro alkanes react with nitrous acid to form _______.

(a)

red solution

(b)

blue solution

(c)

green solution

(d)

yellow solution

Aniline + benzoylchloride \(\overset { NaOH }{ \longrightarrow } \)C₆H₅ - NH - COC₆ H₅ this reaction is known as ______.

(a)

Friedel – crafts reaction

(b)

HVZ reaction

(c)

Schotten – Baumann reaction

(d)

none of these

The method by which aniline cannot be prepared is _________.

(a)

degradation of benzamide with Br₂ / NaOH

(b)

potassium salt of phthalimide treated with chlorobenzene followed by hydrolysis with aqueous NaOH solution.

(c)

reduction of Nitrobenzene with LiAlH₄

(d)

reduction of nitrobenzene by Sn / HCl

On reacting with neutral ferric chloride, phenol gives ______.

(a)

red colour

(b)

violet colour

(c)

dark green colour

(d)

no colouration.

Among the following ethers which one will produce methyl alcohol on treatment with hot HI?

(a)

(H₃C)₃C-O-CH₃

(b)

(CH₃-)₂-CH-CH₂-O-CH₃

(c)

CH₃-(CH₂)₃-O-CH₃

(d)

CH₃-CH₂-\(\underset { \overset { | }{ { CH }_{ 3 } } }{ CH } \)-O-CH₃

The reaction

Can be classified as ______.

(a)

dehydration

(b)

Williams on alcoholsynthesis

(c)

Williamson ether synthesis

(d)

dehydrogenation of alcohol

10.

(CH₃)₃-C-CH(OH) CH₃ \(\overset { con{ H }_{ 2 }{ SO }_{ 4 } }{ \longrightarrow } \)X (major product)

(a)

(CH₃)₃ CCH = CH₂

(b)

(CH₃)₂C = C (CH₃)₂

(c)

CH₂= C(CH₃)CH₂-CH₂- CH₃

(d)

CH₂= C (CH₃) - CH₂- CH₂- CH₃

11.

Which one of the following is the strongest acid.

(a)

2 - nitrophenol

(b)

4 – chlorophenol

(c)

4– nitrophenol

(d)

3 – nitrophenol

12.

An alcohol (x) gives blue colour in victormayer’s test and 3.7g of X when treated with metallic sodium liberates 560 mL of hydrogen at 273 K and 1 atm pressure what will be the possible structure of X?

(a)

CH₃ CH (OH) CH₂CH₃

(b)

CH₃ – CH (OH) – CH₃

(c)

CH₃ – C (OH) – (CH₃)₂

(d)

CH₃- CH₂ –CH (OH) – CH₂– CH₃

13.

Chemical formula of phosgene is_______.

(a)

COCl₂

(b)

CaOCl₂

(c)

CaCO₃

(d)

COCI

14.

Which of the following is commonly used to produce foam in froth floatation process?

(a)

Pine oil

(b)

Cresol

(c)

NaCN

(d)

Xanthate

15.

If 75% of a first order reaction was completed in 60 minutes, 50% of the same reaction under the same conditions would be completed in_______.

(a)

20 minutes

(b)

30 minutes

(c)

35 minutes

(d)

75 minutes

16.

During the decomposition of H₂O₂ to give dioxygen, 48 g O₂ is formed per minute at certain point of time. The rate of formation of water at this point is

(a)

0.75 mol min⁻¹

(b)

1.5 mol min⁻¹

(c)

2.25 mol min⁻¹

(d)

3.0 mol min⁻¹

17.

In a first order reaction x ⟶ y; if k is the rate constant and the initial concentration of the reactant x is 0.1M, then, the half life is_____.

(a)

\(\left( \frac { \log2 }{ k } \right) \)

(b)

\(\left( \frac { 0.693 }{ (0.1)k } \right) \)

(c)

\(\left( \frac { In2 }{ k } \right) \)

(d)

none of these

18.

What is the activation energy for a reaction if its rate doubles when the temperature is raised from 200K to 400K? (R = 8.314 JK^-1 mol^-1)

(a)

234.65 kJ mol^-1

(b)

434.65 kJ mol^-1

(c)

2.305 kJ mol^-1

(d)

334.65 J mol^-1

19.

In a reversible reaction, the enthalpy change and the activation energy in the forward direction are respectively −x kJ mol^-1 and y kJ mol^-1. Therefore, the energy of activation in the backward direction is _______.

(a)

(y-x) kJ mol^-1

(b)

(x+y) J mol^-1

(c)

(x-y) KJ mol^-1

(d)

(x+y) x 10³J mol^-1

20.

The addition of a catalyst during a chemical reaction alters which of the following quantities?

(a)

Enthalpy

(b)

Activation energy

(c)

Entropy

(d)

Internal energy

21.

Schottky defect in a crystal is observed when ______.

(a)

unequal number of anions and anions are missing from the lattice

(b)

Equal number of cations and anions are missing from the lattice

(c)

an ion leaves its normal site and occupies an interstitial site

(d)

no ion is missing from its lattice

22.

If ‘a’ is the length of the side of the cube, the distance between the body centered atom and one corner atom in the cube will be_________.

(a)

\(\left( \cfrac { 2 }{ \sqrt { 3 } } \right) a\)

(b)

\(\left( \cfrac { 4 }{ \sqrt { 3 } } \right) a\)

(c)

\(\left( \cfrac { \sqrt { 3 } }{ 4 } \right) a\)

(d)

\(\left( \cfrac { \sqrt { 3 } }{ 2 } \right) a\)

23.

The radius of an atom is 300pm, if it crystallizes in a face centered cubic lattice, the length of the edge of the unit cell is ________.

(a)

488.5pm

(b)

848.5pm

(c)

884.5pm

(d)

484.5pm

24.

For a first order reaction A ⟶ product with initial concentration x mol L^-1, has a half life period of 2.5 hours. For the same reaction with initial concentration \(\left( \frac { x }{ 2 } \right) \) mol L^-1 the half life is

(a)

(2.5 x 2) hours

(b)

\(\left( \frac { 2.5 }{ 2 } \right) \) hours

(c)

2.5 hours

(d)

Without knowing the rate constant, t_1/2 cannot be determined from the given data

25.

Among the following graphs showing variation of rate constant with temperature (T) for a reaction, the one that exhibits Arrhenius behavior over the entire temperature range is _______.

(a)

(b)

(c)

(d)

both (b) and (c)

26.

CsCl has bcc arrangement, its unit cell edge length is 400pm, its inter atomic distance is ________.

(a)

400pm

(b)

800pm

(c)

\(\sqrt { 3 } \times 100pm\)

(d)

\(\left( \frac { \sqrt { 3 } }{ 2 } \right) \times 400pm\)

27.

The number of unit cells in 8 gm of an element X (atomic mass 40) which crystallizes in bcc pattern is (N_A is the Avogadro number)________.

(a)

6.023 x 10²³

(b)

6.023 x 10²²

(c)

60.23 x 10²³

(d)

\(\left( \frac { 6.023\times { 10 }^{ 23 } }{ 8\times 40 } \right) \)

28.

The ratio of close packed atoms to tetrahedral hole in cubic packing is ________.

(a)

1:1

(b)

1:2

(c)

2:1

(d)

1:4

29.

An ionic compound A_x B_y crystallizes in fcc type crystal structure with B ions at the centre of each face and A ion occupying corners of the cube the correct formula of A_x,B_y is ________.

(a)

(b)

AB₃

(c)

A₃B

(d)

A₈B₆

30.

The stability of +1 oxidation state increases in the sequence ________.

(a)

Al < Ga < In < Tl

(b)

Tl < In < Ga < Al

(c)

In < Tl < Ga < Al

(d)

Ga< In < Al < Tl

31.

The geometry at which carbon atom in diamond are bonded to each other is _______.

(a)

Tetrahedral

(b)

hexagonal

(c)

Octahedral

(d)

none of these

32.

Which of these is not a monomer for a high molecular mass silicone polymer?

(a)

Me₃SiCl

(b)

PhSiCl₃

(c)

MeSiCl₃

(d)

Me₂SiCl₂

33.

When copper is heated with conc HNO₃ it produces ________.

(a)

Cu(NO₃)₂, NO and NO₂

(b)

Cu(NO₃)₂ and N₂O

(c)

Cu(NO₃)₂ and NO₂

(d)

Cu(NO₃)₂ and NO

34.

Which one of the following orders is correct for the bond dissociation enthalpy of halogen molecules?

(a)

Br₂ > I₂ > F₂ > Cl₂

(b)

F₂ > Cl₂ > Br₂ > l₂

(c)

I₂ > Br₂ > Cl₂ > F₂

(d)

Cl₂ > Br₂ > F₂ > I₂

35.

XeF₆ on complete hydrolysis produces________.

(a)

XeOF₄

(b)

XeO₂F₂

(c)

XeO₃

(d)

XeO₂

36.

The molarity of given orthophosphoric acid solution is 2M. Its normality is _______.

(a)

(b)

(c)

(d)

none of these

37.

P₄O₆ reacts with cold water to give _______.

(a)

H₃PO₃

(b)

H₄P₂O₇

(c)

HPO₃

(d)

H₃PO₄

38.

Solid (A) reacts with strong aqueous NaOH liberating a foul smelling gas(B) which spontaneously burn in air giving smoky rings. A and B are respectively_________.

(a)

P₄(red) & PH₃

(b)

P₄(white) & PH₃

(c)

S₈ & H₂S

(d)

P₄(white) & H₂S

39.

Which is true regarding nitrogen?

(a)

least electronegative element

(b)

has low ionisation enthalpy than oxygen

(c)

d- orbitals available

(d)

ability to form pπ-pπ bonds with itself

40.

The basic structural unit of silicates is _______.

(a)

\(\left( SiO_{ 3 } \right) ^{ 2- }\)

(b)

\(\left( SiO_{ 4 } \right) ^{ 2- }\)

(c)

\(\left( Sio \right) ^{ - }\)

(d)

\(\left( SiO_{ 4 } \right) ^{ 4- }\)

41.

Oxidation state of carbon in its hydrides _______.

(a)

(b)

-4

(c)

(d)

42.

Carbon atoms in fullerene with formula C₆₀have _______hybridisation.

(a)

sp³ hybridised

(b)

sp hybridised

(c)

sp² hybridised

(d)

partially sp² and partially sp³ hybridised

43.

Which of the following metals has the largest abundance in the earth’s crust?

(a)

Aluminium

(b)

Calcium

(c)

Magnesium

(d)

Sodium

44.

Which of the following is not true with respect to Ellingham diagram?

(a)

Free energy changes follow a straight line. Deviation occurs when there is a phase change.

(b)

The graph for the formation of CO₂ is a straight line almost parallel to free energy axis.

(c)

Negative slope of CO shows that it becomes more stable with increase in temperature.

(d)

Positive slope of metal oxides shows that their stabilities decrease with increase in temperature.

45.

The incorrect statement among the following is______.

(a)

Nickel is refined by Mond’s process

(b)

Titanium is refined by Van Arkel’s process

(c)

Zinc blende is concentrated by froth floatation

(d)

In the metallurgy of gold, the metal is leached with dilute sodium chloride solution

46.

Extraction of gold and silver involves leaching with cyanide ion. silver is later recovered by_______.

(a)

Distillation

(b)

Zone refining

(c)

Displacement with zinc

(d)

liquation

47.

Which one of the following ores is best concentrated by froth – floatation method?

(a)

Magnetite

(b)

Haematite

(c)

Galena

(d)

Cassiterite

48.

Wolframite ore is separated from tinstone by the process of________.

(a)

Smelting

(b)

Calcination

(c)

Roasting

(d)

Electromagnetic separation

49.

The metal oxide which cannot be reduced to metal by carbon is ________.

(a)

PbO

(b)

Al₂O₃

(c)

ZnO

(d)

FeO

50.

Roasting of sulphide ore gives the gas (A).(A) is a colourless gas. Aqueous solution of (A) is acidic. The gas (A) is______.

(a)

CO₂

(b)

SO₃

(c)

SO₂

(d)

H₂S

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Answers Key:

Multiple Choice Question

50 x 1 = 50

(d)
2-methyl propan-2-ol

(b)
2,4 – dimethyl aniline

(b)
blue solution

(b)
potassium salt of phthalimide treated with chlorobenzene followed by hydrolysis with aqueous NaOH solution.

(b)
violet colour

Cyclic alcolhol → sodium cyclic alkoxide- Williamson ether synthesis.

10.

(CH₃)₂C = C (CH₃)₂

11.

12.

CH₃ CH (OH) CH₂CH₃
2R-OH+ 2Na ⟶ 2RONa + H₂ ↑
2 moles of alcohol gives 1 mole of H₂ which occupies 22.4 L at 273 K and 1 atm number of moles of alcohol
= 2 moles of R -OH/22.4L of H₂ x 560 ml
= 0.05 moles
No of moles = mass/molar mass = m/M
= 3.7/0.05 = 74 g mol^-1
General formula for (R-OH) Cn H_{2n + 1}OH
n(12) + (2n + 1) (1) + 16 + 1 = 74
14n = 74 - 18
14n = 56
n = 56/14 = 4
The "2" alcohol which contains 4 carbon is CH₃ - CH (OH) CH₂ - CH₃

13.

(a)
COCl₂

14.

(a)
Pine oil

15.

t_75% = 2t_50%
t_50% = (t_75%/2) = (60/2) = 30 minutes

16.

(d)
3.0 mol min⁻¹

17.

\(k=\frac { 1 }{ t } ln \frac { \left[ { A }_{ 0 } \right] }{ \left[ A \right] } \)
[A₀] = 0.1: [A] = 0.05
\(k= \left[ \frac { 1 }{ t _{1/2}} \right] ln\left[ \frac { { 0.1 } }{ 0.05 }\right] \)
\(k= \left[ \frac { 1 }{ t _{1/2}} \right] ln (2)\)
t_1/2 = In(2)/K

18.

T₁= 200 K ; k = k₁
T₂ =400 K ; k₁= k₂= 2k₁
log\(\frac {{ k }_{ 2 } }{ { k }_{ 1 } } =\frac { { E }_{ a } }{ 2.303R } \left[ \frac { { T }_{ 2 }-{ T }_{ 1 } }{ { T }_{ 1 }{ T }_{ 2 } } \right] \)
log \( [\frac {{2 k }_{ 1 } }{ { k }_{ 1 } }]\)
\(= \left[ \frac { E_{a} }{ 2.303\times 8.314 JK^{-1} mol^{-1} } \right] \)
\(= \left[ \frac { 400 k - 200K }{200 k \times 400 k } \right] \)
\(E_{a} = \frac{ 0.3010 \times 2.303 \times 8.314 JK^{-1}mol^{-1} \times 200K \times 400 K}{200 K}\)
E_a = 2305 J mol^-1
E_a = 2.305 kJ mol^-1

19.

20.

A catalyst provides a new path to the reaction with low activation energy. i.e., it lowers the activation energy.

21.

(b)
Equal number of cations and anions are missing from the lattice

22.

If a is the length of the side, then the length of the leading diagonal passing through the body centered atom is \(\sqrt{3a} \)
Required distance = \(\left( \cfrac { \sqrt { 3 } }{ 2 } \right) a\)

23.

let edge length = a
\(\sqrt{2a} = 4r\)
\(a = \frac{4 \times 300}{\sqrt {2}}\)
a = 600 x 1.414
a = 848.4 pm

24.

For a first order reaction
t_1/2 = \(\frac { 0.693 }{ { k }}\)
t_1/2 does not depend on the initial concentration and it remains constant (whatever may be the initial concentration)
t_1/2 = 2.5 hrs

25.

\(k=A{ e }^{ -\left( \frac { { E }_{ a } }{ RT } \right) }\)
In k = In A - \({ \left( \frac { { E }_{ a } }{ R } \right) }\) \(\left( \frac { 1 }{ T } \right) \)
This equation is of the form of a straight line y = mx+c
A plot of In k Vs \(\left( \frac { 1 }{ T } \right) \) gives a straight line with a negative slope.

26.

\(3 \sqrt{a} = r_{C_{s+}} + 2r_{C_{f-}} + r_{C_{s+}} \)
\(\left( \frac { \sqrt { 3 } }{ 2 } \right) a = r_{C_{s+}} + r_{C_{f-}} \)
\(\left( \frac { \sqrt { 3 } }{ 2 } \right) \times 400\)= inter ionic distance

27.

In bcc unit cell,
2 atoms = 1 unit cell
Number of atoms in 8 g of element is, Number of moles = 8g / 40 g mol^-1 = 0.2 mol
1 mole contains 6.023 x10²³ atoms
0.2 mole contains 0.2 x 6.023 x 10²³ atoms
[1 unit cell / 2 atoms] x 0.2 x 6.023 x 10²³
= 6.023 x 10²² unit cells.

28.

If number of close packed atoms = N, then
The number of Tetrahedral holes formed = 2N
The number of Octahedral holes formed = N
Therefore, N:2N = 1:2

29.

Number of A ions = N_c/8 = 8/8 = 1
Number of B ions = N_f/2 = 6/2 = 3
Simplest formula = AB₃

30.