Question Set C

cbse 12th Standard Chemistry Solutions Model Questions Papers Study Material - QB365

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Questions:

Multiple Choice Question

45 x 1 = 45

Phenol does not undergo nucleophilic substitution reaction easily due to

(a)

acidic nature of phenol

(b)

partial double bond character of C-OH bond

(c)

partial double bond character of C-C bond

(d)

instability of phenoxide ion

Which of the following molecules has a chiral centre correctly labelled with as asterisk (*)?

(a)

(b)

(c)

(d)

Which reagents are required for one step conversion of chlorobenzene to toluene?

(a)

CH₃Cl/AlCl₃

(b)

CH₃Cl Na, Dry ether

(c)

CH₃Cl/Fe, Dark

(d)

NaNO₂/HCI/0-5°C

'Y' (Major product)

(a)

(b)

(c)

(d)

Identify 'C' in the following:

(a)

Water

(b)

Ethanol

(c)

Propanone

(d)

Cumene hydroperoxide

The shapes of [Cu(NH₃)₄]²⁺ and [Pt(NH₃)₂ Cl₂] are

(a)

square planar, tetrahedral

(b)

tetrahedral, square planar

(c)

square planar, square planar

(d)

tetrahedral, tetrahedral

The stability of Mn²⁺, Fe²⁺,Cr²⁺, Co²⁺ is in order of (At o. of Mn = 25, Fe = 26, Cr = 24, Co = 27)

(a)

Mn²⁺ > Fe²⁺ > Cr²⁺ > CO²⁺

(b)

Fe²⁺ > Mn²⁺ > Co²⁺ > Cr²⁺

(c)

Co²⁺ > Mn²⁺ > Fe²⁺ > Cr²⁺

(d)

Cr²⁺ > Mn²⁺ > Co²⁺ > Fe²⁺

The non-stoichiometric reaction:
2A + B \(\rightarrow\) C+D

Initial conc A	Initial conc of B	Initial rate (Mol L^-1)
0.1 M	0.1 M	1.2 x 10^{- 3}
0.1 M	0.2M	1.2 x 10^{- 3}
0.2 M	0.1 M	2.4 x 10^{- 3}

The rate law for formation of c is

(a)

\(\frac{\mathrm{dc}}{\mathrm{dt}}=k[\mathrm{~A}]\)

(b)

\(\frac{\mathrm{dc}}{\mathrm{dt}}=k[\mathrm{~A}][\mathrm{B}]\)

(c)

\(\frac{\mathrm{dc}}{\mathrm{dt}}=k[\mathrm{~A}]^{2}[\mathrm{~B}]^{1}\)

(d)

\(\frac{\mathrm{dc}}{\mathrm{dt}}=k[\mathrm{~A}][\mathrm{B}]^{2}\)

In which of the following molecules carbon atom marked with asterisk (*) is asymmetric?

(a)

(i), (ii), (iii) and (iv)

(b)

(i), (ii) and (iii)

(c)

(ii), (iii) and (iv)

(d)

(i), (iii) and (iv)

10.

Structure of [Ni(CO)₄] is

(a)

tetrahedral

(b)

square planar

(c)

octahedral

(d)

None of these

11.

The temperature coefficient of a reaction is

(a)

the ratio of rate constant at two temperatures

(b)

the ratio of rate constant differing by 10^opreferably 25^oC and 35^oC

(c)

the rate constant at a fixed temperature

(d)

None of the above

12.

For the reaction,

half-life does not depend on the concentration of the reactant. After 10 min, volume of N₂gas is 20 L and after the completion of reaction, it is 100 L. Hence, rate constant is

(a)

\(\frac{2.303}{10}\) log 5 min^-1

(b)

\(\frac{2.303}{10}\) log 10 min^-1

(c)

\(\frac{2.303}{10}\) log 10 min^-1

(d)

\(\frac{2.303}{10}\) log 20 min^-1

13.

In a reaction, 2x ⟶ y, the concentration of x decreases from 3.0 M to 1.5 Min 4 min. The rate of the reaction is

(a)

0.187 M min^-1

(b)

1.87 M min^-1

(c)

3.75 x 10^-1M min^-1

(d)

0.75 M min^-1

14.

Contact process is used in the formation of sulphur trioxide,
\(2 \mathrm{SO}_{2}(g) + \mathrm{O}_{2}(g) \rightleftharpoons 2 \mathrm{SO}_{3}(g)\)
The rate of reaction can be expressed as
\(\frac{-\Delta\left(\mathrm{O}_{2}\right]}{\Delta t}=2.5 \times 10^{-4} \mathrm{~mol} \mathrm{~L}^{-1} \mathrm{~s}^{-1}\)
Then rate of disappearance of [SO₂]will be

(a)

\(50.0 \times 10^{-5} \mathrm{~mol} \mathrm{~L}^{-1} \mathrm{~s}^{-1}\)

(b)

\(3.75 \times 10^{-4} \mathrm{~mol} \mathrm{~L}^{-1} \mathrm{~s}^{-1}\)

(c)

\( 2.5 \times 10^{-4} \mathrm{~mol} \mathrm{~L}^{-1} \mathrm{~s}^{-1}\)

(d)

\(4.12 \times 10^{-4} \mathrm{~mol} \mathrm{~L}^{-1} \mathrm{~s}^{-1}\)

15.

Given the standard electrode potentials,
E^o_Fe²⁺_/Fe= - 0.44 V
and E^o_H+/_O2/_H2O= 1.23 V
Calculate the E⁰_cell of the corrosion.

(a)

- 0.79 V

(b)

- 1.67 V

(c)

1.67 V

(d)

+ 0.79 V

16.

Knowing that the chemistry of lanthanoids (Ln) is dominated by its +3 oxidation state, which of the following statements is incorrect ?

(a)

The ionic sizes of Ln (III) decrease in general with increasing atomic number.

(b)

Ln (III) compounds are generally colourless.

(c)

Ln (III) hydroxides are mainly basic in character

(d)

Because of the large size of the Ln (III) ions, the bonding in its compounds is predominantly ionic in character.

17.

Identify the incorrect statement among the following :

(a)

Shielding power of 4f electrons is quit weak

(b)

There is a decrease in the radii of the atoms or ions as one proceeds from La to Lu

(c)

Lanthanoid contraction is the accumulation of successive shrinkages.

(d)

As a result of lanthanoid contraction, the properties of 4d series of the transition elements have no similarities with the 5d series of the elements.

18.

Which of the following statements about the interstitial compounds is incorrect ?

(a)

They retain metallic conductivity

(b)

They are chemically reactive

(c)

They are much harder than the pure metal

(d)

They have higher melting points than the pure metal

19.

The value of 'spin only' magnetic moment for one of the following configurations is 2.84 BM. The correct one is

(a)

d ⁴ (in strong ligand field)

(b)

d ⁴ ( in weak ligand field)

(c)

d ³ (in weak as well as strong fields)

(d)

d ⁵ (in strong ligand field)

20.

Among the following the one which reacts most readily with ethanol is

(a)

p-nitrobenzyl

(b)

p-chlorobenzyl

(c)

p-methoxybenzyl bromide

(d)

p-methylbenzyl bromide

21.

In the reaction, CH₃COOH \(\overset{LiAlH_4}\longrightarrow\) A \(\overset{PCl_4}\longrightarrow\) B \(\overset{Alc.KOH}\longrightarrow\)C, the product C is

(a)

acetyl chloride

(b)

acetaldeyde

(c)

acetylene

(d)

ethylene

22.

In the following sequence of reactions, CH₃-Br \(\overset{KCN}\longrightarrow\) A \(\overset{H_3O^+}\longrightarrow\) B \(\overset { LiAlH_{ 4 } }{ \underset { ether }{ \longrightarrow } } \) C the end product (c) is

(a)

acetone

(b)

methane

(c)

acetaldehyde

(d)

ethyl alcohol

23.

Which of the esters shown,after reduction with LiAlH₄ and aqueous work up, will yield two molecules of only a single alcohol?

(a)

C₆H₅COOC₆H₅

(b)

CH₃CH₂COOCH₂CH₃

(c)

C₆H₅COOCH₂C₆H₅

(d)

CH₃COOCH₃

24.

Which of the following compounds can be classified as aryl halides?

(a)

p-ClC₆H₄CH₂CH(CH₃)₂

(b)

p-CH₃CHCl(C₆H₄)CH₂CH₃

(c)

o-BrH₂C-C₆H₄CH(CH₃)CH₂CH₃

(d)

C₆H₅-Cl

25.

Best reagent for nuclear iodination of aromatic compounds is

(a)

KI/CH₃COCH₃

(b)

I₂/CH₃CN

(c)

KI/CH₃COOH

(d)

I₂/HNO₃

26.

The synthesis of alkyl flurides is best acomplished by

(a)

Finekelstein reaction

(b)

Swarts reaction

(c)

free radical fluourination

(d)

Sandmeyer's reaction

27.

In the presence of peroxide, hydrogen chloride and hydrogen iodide do not give anti-Markovinikov's addition to alkenes because

(a)

both are highly ionic

(b)

one is oxidising and the other is reducing

(c)

one of the steps are exothermic in both the cases

(d)

all the steps are exothermic in both the reactions.

28.

Indicate the complex ion which shows geometrical isomerism.

(a)

[Cr(H₂O)₄Cl₂]⁺

(b)

[Pt(NH₃)₃Cl]

(c)

[Co(NH₃)₆]³⁺

(d)

[Co(CN)₅(NC)]^3-

29.

Among the following complexes (K-P) K₃[Fe(CN)₆] (K), [Co(NH₃)₆]Cl₃ (L), Na₃[Co(oxalate)₃](M), [Ni(H₂O)₆]Cl₂ (N), K₂[Pt(CN)₄] (O) and [Zn(H₂O)₆] (NO₃)₂ (P) the diamagnetic complexes are

(a)

K, L, M, N

(b)

K, M, O, P

(c)

L, M, O, P

(d)

L, M, N, O

30.

Which of the following complex species is not expected to exhibit optical isomerism?

(a)

[Co(en)(NH₃)₂Cl₂]⁺

(b)

[Co(en)₃]³⁺

(c)

[Co(en)₂Cl₂]⁺

(d)

[Co(NH₃)₃Cl₃]

31.

Which of the following statements are correct concerning redox properties ?
(i) A metal M for which E⁰ for the half life reaction \({ M }^{ n+ }+{ ne }^{ - }\rightleftharpoons M\) is very negative will be a good reducing agent.
(ii) The oxidizing power of the halogen decreases from chlorine to iodine
(iii) The reducing power of hydrogen halides increases from hydrogen chloride to hydrogen iodide

(a)

(i), (ii) and (iii)

(b)

(i) and (ii)

(c)

(i) only

(d)

(ii) and (iii) only

(e)

(iii) only

32.

For the given complex [CoCl₂ (en) (NH₃)₂]⁺, the number of geometrical isomers, the number of optical isomers and total number of isomers of all type possible respectively are

(a)

2, 2 and 4

(b)

2, 2 and 3

(c)

2, 0 and 2

(d)

0, 2 and 2

33.

The limiting molar conductivities of HCl, CH₃COONa and NaCl are respectively 425, 90 and 125 mho cm² mol^-1 at 25°C. The molar conductivity of 0.1 M CH₃COOH solution is 7.8 mho cm² mol^-1 at the same temperature. The degree of dissociation of 0.1 M acetic acid solution at the same temperature is

(a)

0.10

(b)

0.02

(c)

0.15

(d)

0.03

(e)

0.20

34.

Which of the following statement is correct? (CFSE= Crystal Field Splitting Energy)

(a)

Lower CFSE favours formation of low spin complex

(b)

Higher CFSE favours formation of high spin complex

(c)

A particular metal ion in a particular oxidation state can form either diamagnetic complexes only or paramagnetic complexes only.

(d)

t_2g orbitals are three fold degenerate while e_g orbitals are two fold degenerate

35.

The activation energy of a reaction can be determined from the slope of which of the following graph ?

(a)

In k vs \(\frac {1}{T}\)

(b)

\(\frac {T}{In k} vs \frac {1}{T}\)

(c)

In k vs T

(d)

\(\frac {In k} {T}\) vs T

36.

Large number of oxidation states are exhibited by the actinoids than those by the lanthanoids, the main reason being

(a)

more energy difference between 5f and 6d than between 4f and 5d orbitals

(b)

more reactive nature of the actinoids than the lanthanoids

(c)

4f orbitals more diffused than the 5 f orbitals

(d)

lesser energy difference between 5f and 6d than between 4f and 5d orbitals

37.

Name a member of lanthanide series which is well known to exhibit + 4 oxidation state :

(a)

(b)

(c)

(d)

38.

Which one of the following aqueous solutions will have the lower freezing point?

(a)

0.1 molal solution of urea

(b)

0.1 molal solution of acetic acid

(c)

0.1 molal solution of sodium chloride

(d)

0.1 molal solution of calcium chloride

39.

\(6.02\times { 10 }^{ 20 }\) molecules of urea are present in 100 mL of its solution. The concentration of the solution is

(a)

0.02 M

(b)

0.01 M

(c)

0.001 M

(d)

0.1 M

40.

When ethyl acetate was hydrolysed in presence of 0.1 N HCI, the rate constant was found to be 5.40 \(\times\) 10^-5 s^-1 . From these values we can say that

(a)

H₂SO₄ is stronger than HCI

(b)

H₂SO₄ is weaker than HCI

(c)

Both the acids have equal strength

(d)

The data is insufficient to compare the strengths of HCI and H₂SO₄

41.

Consider the following four electrodes

P = Cu²⁺ (0.0001 M)/Cu (s)	Q = Cu²⁺ (0.1 M)/Cu (s)
R = Cu²⁺ (0.01 M)/Cu (s)	S = Cu²⁺ (0.001 M)/Cu (s)

If the standard electrode potential of Cu²⁺/Cu is + 0.34 V, the reduction potentials in volts of the above electrodes follow the order :

(a)

P > S > R > Q

(b)

S > R > Q > P

(c)

R > S > Q > P

(d)

Q > R > S > P

42.

A dilute aqueous solution of Na₂ SO₄ is electrolysed using platinum electrodes. The products at the anode and cathode are

(a)

O₂ , H₂

(b)

SO₂ , Na

(c)

O₂ , Na

(d)

S₂ O₈^2- , H₂

43.

Which following factor (s) affect the solubility of a gaseous solute in the fixed volume of liquid solvent ?
(i) nature of solute
(ii) temperature
(iii) pressure

(a)

(i) and (iii) at constant T

(b)

(i) and (ii) at constant P

(c)

(ii) and (iii) only

(d)

(iii) only

44.

K_H value for Ar(g), CO₂(g), HCHO (g) and CH₄ (g) are 4.39,1.67,1.83 x 10^-5 and 0.413 respectively. Arrange these gases in the order of their increasing solubility.

(a)

\( \mathrm{HCHO}<\mathrm{CH}_4<\mathrm{CO}_2<\mathrm{Ar}\)

(b)

\( \mathrm{HCHO}<\mathrm{CO}_2<\mathrm{CH}_4<\mathrm{Ar} \)

(c)

\( \mathrm{Ar}<\mathrm{CO}_2<\mathrm{CH}_4<\mathrm{HCHO} \)

(d)

\( \mathrm{Ar}<\mathrm{CH}_4<\mathrm{CO}_2<\mathrm{HCHO} \)

45.

Maximum amount of a solid solute that can be dissolved in a specified amount of a given liquid solvent does not depend upon __________________.

(a)

Temperature

(b)

Nature of solute

(c)

Pressure

(d)

Nature of solvent

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Answers Key:

Multiple Choice Question

45 x 1 = 45

(b)
partial double bond character of C-OH bond

(b)
CH₃Cl Na, Dry ether

(a)
Mn²⁺ > Fe²⁺ > Cr²⁺ > CO²⁺

(a)
\(\frac{\mathrm{dc}}{\mathrm{dt}}=k[\mathrm{~A}]\)

(b)
(i), (ii) and (iii)

10.

(a)
tetrahedral

11.

(b)
the ratio of rate constant differing by 10^opreferably 25^oC and 35^oC

12.

(a)
\(\frac{2.303}{10}\) log 5 min^-1

13.

(a)
0.187 M min^-1

14.

15.

16.

(b)
Ln (III) compounds are generally colourless.

17.

(d)
As a result of lanthanoid contraction, the properties of 4d series of the transition elements have no similarities with the 5d series of the elements.

18.