Question Set B

Tamilnadu 12th Standard Chemistry p - Block Elements - II Important Questions Study Material - QB365

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Questions:

Multiple Choice Question

50 x 1 = 50

For the reaction \({ N }_{ 2 }{ O }_{ 5 }\left( g \right) \longrightarrow { 2NO }_{ 2 }\left( g \right) +\frac { 1 }{ 2 } { O }_{ 2 }\left( g \right) \) value of rate of disappearance of N₂O₅is given as 6.5 x 10^-2 mol L^-1s^-1. The rate of formation of NO₂ and O₂ is given respectively as_____.

(a)

(3.25 x 10^-2 mol L^-1s^-1) and (1.3 x 10^-2 mol L^-1s^-1)

(b)

(1.3 x 10^-2 mol L^-1s^-1) and (3.25 x 10^-2 mol L^-1s^-1)

(c)

(1.3 x 10^-1mol L^-1s^-1) and (3.25 x 10^-2 mol L^-1s^-1)

(d)

None of these

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

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

For a reaction Rate = k[acetone]^3/2 then unit of rate constant and rate of reaction respectively is _______.

(a)

(mol L^-1 S^-1),(mol^1/2L^1/2S^-1)

(b)

(mol^-1/2L^1/2s^-1),(mol L^-1s^-1)

(c)

(mol^1/2L^1/2s^-1),(mol L^-1s^-1)

(d)

(mol L s^-1),(mol^1/2L^1/2s)

Potassium has a bcc structure with nearest neighbor distance 4.52 \(\overset{o}{A}\). Its atomic weight is 39. its density will be_______.

(a)

915 kg m^-3

(b)

2142 kg m^-3

(c)

452 kg m^-3

(d)

390 kg m^-3

The fraction of total volume occupied by the atoms in a simple cubic is ________.

(a)

\(\left( \frac { \pi }{ 4\sqrt { 2 } } \right) \)

(b)

\(\left( \frac { \pi }{ 6 } \right) \)

(c)

\(\left( \frac { \pi }{ 4 } \right) \)

(d)

\(\left( \frac { \pi }{ 3\sqrt { 2 } } \right) \)

A solid compound XY has NaCl structure if the radius of the cation is 100pm, the radius of the anion will be ________.

(a)

\(\left( \frac { 100 }{ 0.414 } \right) \)

(b)

\(\left( \frac { 0.732 }{ 100 } \right) \)

(c)

100 x 0.414

(d)

\(\left( \frac { 0.414 }{ 100 } \right) \)

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

A zero order reaction X ⟶ Product, with an initial concentration 0.02M has a half life of 10 min. if one starts with concentration 0.04M, then the half life is

(a)

10 s

(b)

5 min

(c)

20 min

(d)

cannot be predicted using the given information

10.

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)

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

11.

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

12.

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

13.

Choose the correct statement.

(a)

Square planar complexes are more stable than octahedral complexes

(b)

The spin only magnetic moment of [Cu(Cl)₄]^2- is BM and it has square planar structure.

(c)

Crystal field splitting energy \(\left( { \Delta }_{ 0 } \right) \) [FeF₆]^4- is higher than the \((\Delta _{ 0 })\) of [Fe(CN)₆]^4-

(d)

crystal field stabilization energy of [V(H₂O)₆]²⁺ is higher than the crystal field stabilization of [Ti(H₂O)₆]²⁺

14.

Fac-mer isomerism is shown by _______.

(a)

[CO(en)₃]³⁺

(b)

[Co(NH₃)₄(Cl)₂]⁺

(c)

[Co(NH₃)₃(Cl)₃]

(d)

[Co(NH₃)₅Cl]SO₄

15.

Formula of tris(ethane-1, 2-diamine)iron(II)phosphate _______.

(a)

[Fe(CH₃-CH(NH₂)₂)₃](PO₄)₃

(b)

[Fe(H₂N-CH₂-CH₂-NH₂)₃](PO₄)

(c)

[Fe(H₂N-CH₂-CH₂-NH₂)₃](PO₄)₂

(d)

[Fe(H₂N-CH₂-CH₂-NH₂)₃]₃(PO₄)₂

16.

Which one of the following pairs represents linkage isomers?

(a)

[Cu(NH₃)₄][PtCl₄] and [Pt(NH₃)₄][CuCl₄]

(b)

[Co(NH₃)₅(NO₃)]SO₄ and [Co(NH₃)₅(ONO)]

(c)

[Co(NH₃)₄(NCS)₂]Cl and [Co(NH₃)₄(SCN)₂]Cl

(d)

both (b) and (c)

17.

Which one of the following will give a pair of enantiomorphs?

(a)

[Cr(NH₃)₆][Co(CN)₆]

(b)

[Co(en)₂Cl₂]Cl

(c)

[Pt(NH₃)₄][PtCl₄]

(d)

[Co(NH₃)₄Cl₂]NO₂

18.

IUPAC name of the complex K₃[Al(C₂O₄)₃] is _______.

(a)

potassium trioxalatoaluminium (III)

(b)

possium trioxalatoaluminate (II)

(c)

potassium trisoxalatoaluminate (III)

(d)

potassium trioxalatoaluminate (III)

19.

An excess of silver nitrate is added to 100ml of a 0.01M solution of Pentaaquachlorochromium (III)chloride. The number of moles of AgCl precipitated would be _______.

(a)

0.02

(b)

0.002

(c)

0.01

(d)

0.2

20.

Which of the following lanthanoid ions is diamagnetic?

(a)

Eu²⁺

(b)

Yb²⁺

(c)

Ce²⁺

(d)

Sm²⁺

21.

Permanganate ion changes to ________ in acidic medium.

(a)

MnO₄²⁻

(b)

Mn²⁺

(c)

Mn³⁺

(d)

MnO₂

22.

The correct order of increasing oxidizing power in the series _______.

(a)

VO₂⁺ < Cr₂O₇^2- < MnO₄^-

(b)

Cr₂O₇^2- < VO₂⁺ < MnO₄^-

(c)

Cr₂O₇^2- < MnO₄^- < VO₂⁺

(d)

MnO₄^- < Cr₂O₇^2- < VO₂⁺

23.

The catalytic behaviour of transition metals and their compounds is ascribed mainly due to _______.

(a)

their magnetic behaviour

(b)

their unfilled d orbitals

(c)

their ability to adopt variable oxidation states

(d)

their chemical reactivity

24.

Which one of the following ions has the same number of unpaired electrons as present in V³⁺?

(a)

Ti³⁺

(b)

Fe³⁺

(c)

Ni²⁺

(d)

Cr³⁺

25.

Among the transition metals of 3d series, the one that has highest negative \(\left( \frac { M^{ 2+ } }{ M } \right) \) standard electrode potential is _______.

(a)

(b)

(c)

(d)

26.

Sc (Z = 21) is a transition element but Zinc (z = 30) is not because _______.

(a)

both Sc³⁺ and Zn²⁺ ions are colourless and form white compounds

(b)

In case of Sc, 3d orbital are partially filled but in Zn these are completely filled

(c)

last electron as assumed to be added to 4s level in case of zinc

(d)

both Sc and Zn do not exhibit variable oxidation states

27.

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

28.

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

29.

Which of the following is strongest acid among all?

(a)

(b)

(c)

HBr

(d)

HCl

30.

Most easily liquefiable gas is _______.

(a)

(b)

(c)

(d)

31.

The basicity of pyrophosphorous acid ( H₄P₂O₅) is _______.

(a)

(b)

(c)

(d)

32.

On hydrolysis, PCl₃ gives________.

(a)

H₃PO₃

(b)

PH₃

(c)

H₃PO₄

(d)

POCl₃

33.

An element belongs to group 15 and 3^rdperiod of the periodic table, its electronic configuration would be_______.

(a)

1s² 2s² 2p⁴

(b)

1s² 2s² 2p³

(c)

1s² 2s² 2p⁶ 3s² 3p²

(d)

1s² 2s² 2p⁶ 3s² 3p³

34.

The basic structural unit of silicates is _______.

(a)

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

(b)

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

(c)

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

(d)

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

35.

Carbon atoms in fullerene with formula C₆₀have _______hybridisation.

(a)

sp³ hybridised

(b)

sp hybridised

(c)

sp² hybridised

(d)

partially sp² and partially sp³ hybridised

36.

In diborane, the number of electrons that accounts for banana bonds is ________.

(a)

six

(b)

two

(c)

four

(d)

three

37.

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

(a)

Aluminium

(b)

Calcium

(c)

Magnesium

(d)

Sodium

38.

Which among the following is not a borane?

(a)

B₂H₆

(b)

B₃H₆

(c)

B₄H₁₀

(d)

none of these

39.

Boric acid is an acid because its molecule________.

(a)

contains replaceable H⁺ ion

(b)

gives up a proton

(c)

combines with proton to form water molecule

(d)

accepts OH^- from water, releasing proton.

40.

Which of the following reduction is not thermodynamically feasible?

(a)

\({ Cr }_{ 2 }{ O }_{ 3 }+2Al\longrightarrow { Al }_{ 2 }{ O }_{ 3 }+2Cr\)

(b)

\(\mathrm{Al}_2 \mathrm{O}_3+2 \mathrm{Cr} \longrightarrow \mathrm{Cr}_2 \mathrm{O}_3+2 \mathrm{Al}\)

(c)

\(3Ti{ O }_{ 2 }+4Al\longrightarrow 2A{ l }_{ 2 }{ O }_{ 3 }+3Ti\)

(d)

none of these

41.

Which of the following plot gives Ellingham diagram

(a)

\(\Delta S \ \text{Vs} \ T\)

(b)

\(\Delta { G }^{ 0 }\ \text{Vs} \ T\)

(c)

\(\Delta { G }^{ 0 }\ \text{Vs} \ \frac { 1 }{ T } \)

(d)

\(\Delta { G }^{ 0 }\ \text{Vs} \ { T }^{ 2 }\)

42.

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

43.

Considering Ellingham diagram, which of the following metals can be used to reduce alumina?

(a)

(b)

(c)

(d)

44.

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

45.

In the extraction of aluminium from alumina by electrolysis, cryolite is added to_______.

(a)

Lower the melting point of alumina

(b)

Remove impurities from alumina

(c)

Decrease the electrical conductivity

(d)

Increase the rate of reduction

46.

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

(a)

Magnetite

(b)

Haematite

(c)

Galena

(d)

Cassiterite

47.

Which one of the following is not feasible

(a)

Zn_(s) + Cu²⁺_(aq) \(\rightarrow\) Cu_(s) + Zn²⁺_(aq)

(b)

Cu_(s)+ Zn²⁺_(aq)\(\rightarrow\) Zn_(s) + Cu²⁺_(aq)

(c)

Cu_(s) + 2Ag⁺_(ag)\(\rightarrow\) 2Ag_(s) + Cu²⁺_(aq)

(d)

Fe_(s) + Cu²⁺_(aq) \(\rightarrow\) Cu_(s)+ Fe²⁺_(aq)

48.

Wolframite ore is separated from tinstone by the process of________.

(a)

Smelting

(b)

Calcination

(c)

Roasting

(d)

Electromagnetic separation

49.

Which of the following statements, about the advantage of roasting of sulphide ore before reduction is not true?

(a)

\(\Delta { G }_{ f }^{ 0 }\) of sulphide is greater than those for CS₂ and H₂S

(b)

\(\Delta { G }_{ r }^{ 0 }\) is negative for roasting of sulphide ore to oxide

(c)

Roasting of the sulphide to its oxide is thermodynamically feasible

(d)

Carbon and hydrogen are suitable reducing agents for metal sulphides

50.

Which of the metal is extracted by Hall-Heroult process?

(a)

(b)

(c)

(d)

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Answers Key:

Multiple Choice Question

50 x 1 = 50

Rate \(=\frac { d\left[ { N_2O_5 } \right] }{ dt } =\frac { 1 }{ 2 } =\frac { d\left[ { NO}_{ 2 } \right] }{ dt } =\frac { 2d\left[ { O }_{ 2 } \right] }{ dt } \)
Given that \(=\frac { d\left[ { N_2O_5 } \right] }{ dt } \) =6.5 x 10^-2 mol L^-1 s^-1
\(=\frac { d\left[ { NO}_{ 2 } \right] }{ dt }\) =2 x 6.5 x 10^-2= 1.3 x 10^-1mol L^-1 s^-1
\(=\frac { d\left[ { O}_{ 2 } \right] }{ dt }\)\(=\frac{6.5 \times 10^{-2}}{2}\) = 3.25 x 10^-2 mol L^-1s^-1

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

Rate = k[A]ⁿ
Rate = \(\frac{-\mathrm{d}[\mathrm{A}]}{\mathrm{dt}}\)
unit of rate = \(\frac{mol L^{-1}}{s}\)=mol L^-1/s^-1
unit of rate constant
\(=\frac{ (mol{ L }^{ -1 }{ S }^{ -1 }) }{ ({ mol }{ L }^{ -1 })^n } \)
= mol^1-nL^n-1s^-1
in the case
rate = k [Acetone]^3/2
n = 3/2
= mol^1-(3/2)L^(3/2)-1s^-1
(mol^-(1/2)L^(1/2)s^-1).

\(\rho=\frac{\mathrm{n} \times \mathrm{M}}{\mathrm{a}^{3} \mathrm{~N}_{\mathrm{A}}}\)
For bcc n =2, M = 39 nearest distance 2r = 4.52 A⁰
\(a =\frac{4r}{\sqrt {3}} = \frac { 2\times 4.52 \times 10^{-10} }{ \sqrt{3}} \)
\(\rho =\frac { {( 5.21\times 10^{-10})^{ 3 }} \times (6.023 \times 10^{-23}) }{ 2 \times 39} \)
ρ = 915 kgm^-3

(b)
\(\left( \frac { \pi }{ 6 } \right) \)

For a fcc structure = r_x+ / r_y- = 0.414
Given that r_x⁺ = 100 pm
r_y = 100pm/0.414

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

for n ≠ 1 t_1/2 = \(\frac{2^{n-1} -1}{(n- 1) k[A_{0}]^{-1}}\)
for n = 0; t_1/2 = \(\frac{1}{2 k[A_{0}]^{-1}}\)
t_1/2 = \(\frac{[A_{0}]}{2 k}\)
t_1/2 α [A₀] ...(1)
Given [A₀] = 0.002 M; t_1/2 = 10 min
[A₀] = 0.04M; t_1/2 = ?
Substitute in (1)
10 min α 0.02 M...(2)
t_1/2 α 0.04M ....(3)
(3)(2)
⇒ t_1/2 / 10 min
= 0.04 M/0.02 M
t_1/2 = 2 x 10 min = 20 min

10.

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.

11.

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

12.

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

13.

(d)
crystal field stabilization energy of [V(H₂O)₆]²⁺ is higher than the crystal field stabilization of [Ti(H₂O)₆]²⁺

14.

15.

[Fe(H₂N-CH₂-CH₂-NH₂)₃]₃(PO₄)₂
[Fe(en)₃]²⁺(\(PO_{4}^{3-}\))

16.

(a) coordination isomers
(b) no isomerism ( different molecular formula)
(c)⬅NCS; ⬅SCN coordinating atom differs : linkage isomers

17.

Complexes given in other options (a), (c) and (d) have symmetry elements and hence they are optically inactive.

18.

(d)
potassium trioxalatoaluminate (III)

19.

The complex is [M(H₂O)₅Cl]Cl₂
1000 ml of 1 M solution of the complex gives 2 moles of Cl^- ions 1000 ml of 0.01 M solution of the complex will give
\(\frac{100 ml \times 0.01M \times 2Cl^-}{1000 ml \times 1M}\)
= 0.002 moles of Cl^- ions

20.

Yb²⁺ - 4f¹⁴ - no unpaired electrons - diamagnetic

21.

MnO^-₄ + 8H⁺ + 5e^-→ Mn²⁺ + 4H₂O

22.

+5 +6 +7
VO₂⁺ < Cr₂O₇^2- < MnO₄^-
Greater the oxidation state, higher is the oxidising power.

23.

24.

25.