Question Set C

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

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Questions:

Generic 3

5 x 3 = 15

For a reaction, P⟶Q, the rate becomes 8 times when concentration of P is doubled. What is the order of the reaction?

(a) What type of isomerism is shown by the complex [Co(en)₃]CI₃?
(b) Write the hybridisation and magnetic character of [Co(C₂O₄)₃]^3-. (Atomic number of Co = 27)
(c) Write IUPAC name of the following complex [Cr(NH₃)₃CI₃].

Explain the following observations:
(i) With the same d-orbital configuration (d⁴), Cr²⁺ ion is a reducing agent while Mn³⁺ ion is an oxidising agent.
(ii) Cu⁺ ion is not stable in aqueous solutions.
(iii) Among the 3d series of transition elements, the largest number of oxidation states are exhibited by manganese.

Nitric oxide,NO reacts with oxygen to nitrogen dioxide:2NO(g) + O₂(g)\(\longrightarrow\)2NO₂(g) What is the predicted rate law, if the mechnism is:NO + O₂\(\overset { k }{ \rightleftharpoons } \)NO₃(fast)NO + NO₃\(\overset { { k }_{ 1 } }{ \longrightarrow } \)NO₂ + NO₂(slow).

Explain the following:
(i) The transition elements have great tendency for complex formation.
(ii) There is a gradual decrease in the atomic sizes of transition elements in a series with increasing atomic numbers.
(iii) Lanthanum and Lutetium do not show colouration in solutions.
(At. No : La = 57, Lu = 71)

Multiple Choice Question

10 x 1 = 10

Which of the following statements related to lanthanoids is incorrect?

(a)

Eu shows + 2 oxidation state

(b)

Pr(OH)₃ to Lu(OH)₃, basicity decreases

(c)

All lanthanoids more reactive than Al

(d)

Ce⁴⁺ is used as oxidising agent

If conc. of reactant' A' is increased 10 times and rate of reaction becomes 100 times. What is order with respect to 'A'?

(a)

(b)

(c)

(d)

The variability of oxidation state

(a)

is a characteristic of transition elements

(b)

arises out of incomplete filling of d-orbitals in such a way that their oxidation states differ from each other by unity

(c)

differs from the variability of oxidation states of non-transition elements, where the oxidation states normally differ by two unit.

(d)

All of the above are true

KMnO₄ acts as an oxidising agent in alkaline medium. When alkaline KMnO₄ is treated with KI, iodide ion is oxidised to ............ .

(a)

I₂

(b)

IO^-

(c)

\({ IO }_{ 3 }^{ - }\)

(d)

\({ IO }_{ 4 }^{ - }\)

10.

A, B and C are three complexes of chromium (III) with the empirical formula H₁₂O₆Cl₃Cr. All the three complexes have water and chloride ions as ligands. Complex A does not react with conc. H₂SO₄ whereas complexes B and C lose 6.75% and 13.5% of their original weight respectively, on treatment with concentrated H₂SO₄.
The complex A is

(a)

[Cr(H₂O)₄(H)₄(O)₂]Cl₃

(b)

[Cr(H₂O₅)₅(H)₂(O)]Cl₃

(c)

[Cr(H₂O)₆]Cl₃

(d)

[Cr(H₂O)₅Cl]Cl₂.H₂O

11.

The CFSE for octahedral [CoCl₆]^4- is 18,000 cm^-1. The CFSE for tetrahedral [CoCl₄]^2- will be

(a)

18,000 cm^-1

(b)

16,000 cm^-1

(c)

8,000 cm^-1

(d)

20,000 cm^-1

12.

Prussian blue is obtained by mixing together aqueous solution of Fe³⁺ salt with

(a)

Ferricyanide

(b)

Ferocyanide

(c)

Hydrogen cyanide

(d)

Sodium cyanide

13.

Which one of the following is a tridentate ligand?

(a)

NO^-₂

(b)

oxalate ion

(c)

glycinate ion

(d)

dien

14.

For the reaction A + 2 B \(\longrightarrow\) C, the reaction rate is doubled if the increased by four times when concentration of both A and B are increased by four times. The order of reaction is

(a)

(b)

(c)

(d)

15.

For the reaction A + B \(\longrightarrow\) C + D, doubling the concentration of both the reactants increases the reaction rate by 8 times and doubling the concentration of only B simply doubles the reaction rate. The rate law is given as

(a)

r = k[A]^1/2 [B]^1/2

(b)

r = k[A] [B]²

(c)

r = k[A]²[B]

(d)

r = k[A] [B}

Generic 5

4 x 5 = 20

16.

(a) Consider the reaction R \(\rightarrow\) P for which the change in concentration of R with time is shown by the following graph:

(i) Predict the order of the reaction.
(ii) What does the slope of the curve indicate?
(b) The rate of reaction quadruples when temperature changes from 293 K to 313 K. Calculate E_a assuming that it does not change with time. [R = 8.314 JK^-1 mol^-1)

17.

Co-ordination compounds have an important role in the field of medicines. Out of these, the compound cis-platin is quite effective against cancer. It inhibits the growth of tumors leading to cancer.
(i) What is the chemical formula and name of the complex?
(ii) How does it behave as an anti cancer agent?
(iii) Why is trans-isomer not effective?
(iv) What is the value associated with the use of cis platin?

18.

Lokesh is a social worker. A milkman in the village has been complaining that a factory in his nearby area dumps chemical waste in his field which has become a major cause of decreasing productivity. Lokesh visited that place and found after analysis that the major waste was potassium permanganate which is being absorbed by the soil. He advised the factory people that they should treat potassium permanganate solution before dumping it into the drain.
Comment in brief:
(i) About the environmental values displayed by Lokesh.
(ii) Write balanced chemical equations for the two reactions showing oxidizing nature of potassium permanganate.

19.

Using crystal field theory, draw energy level diagram, write electronic configuration of the central metal atom/ion and determine the magnetic moment value in the following :
(i) \([CoF_6]^{3-}, [Co(H_2O)_6]^{2+},[Co(CN)_6]^{3-}\)
(ii) \([FeF_6]^{3-}, \ [Fe(H_2O)_6]^{2+}, [Fe(CN)_6]^{4-}\).

Generic 2

5 x 2 = 10

20.

Give the examples of two coordination complexes where central metal atom has coordination number (i) 4 (ii) 6

21.

Complete the following chemical equations:
\((i)Cr_2O_7^-(aq)+C_2O_4^{2-}(aq)+H^+(aq)⟶\)
\((ii)MnO_4^-(aq)+Fe^{2+}(aq)+H^+(aq)⟶\)

22.

Why is europium (II) more stable than cerium (II)?

23.

Why does \({ NH }_{ 3 }\)readily form complexes but \({ { NH }_{ 4 } }^{ + }\)does not? Explain.

24.

For a reaction A \(\longrightarrow \) B, the rate of reaction becomes twenty seven times when the concentration of A is increased three ttimes. what is the order of the reaction?

Assertion and reason

2 x 1 = 2

25.

Assertion: Cu cannot liberate hydrogen from acids.
Reason: Because it has positive electrode potential.
Codes:
a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
b) Both assertion and reason are true but the reason is not the correct explanation of assertion.
c) Assertion is not true but the reason is true.
d) Both assertion and reason are false.

26.

Assertion: Zinc is used in the galvanisation of iron.
Reason: Its coating on iron articles increases their life by protecting them from rusting.
Codes:
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.

Case Study Questions

2 x 4 = 8

27.

For the reaction : 2NO_(g) + Cl_2(g) → 2NOCl_(g) the following data were collected. All the measurements were taken at 263 K.

1.The molecularity of the reaction is
(a) 1
(b) 2
(c) 3
(d) 4
2.The expression for rate law is
(a) r = k[NO]Cl₂
(b) r = k[NO]²[Cl₂]
(c) r = k[NO][Cl₂]²
(d) r = k[NO]²[Cl₂]²
3.The overall order of the reaction is
(a) 2
(b) 0
(c) 1
(d) 3
4.The value of rate constant is
(a) 150.32 M^–2 min^–1
(b) 200.08 M^–1 min^–1
(c) 177.77 M^–2 min^–1
(d) 155.75 M^–1min^–1
5.The initial rate of disappearance of Cl₂ in experiment 4 is
(a) 1.75 M min^–1
(b) 3.23 M min^–1
(c) 2.25 M min^–1
(d) 2.77 M min^–1

28.

Read the passage given below and answer the following questions:
Arrangement of ligands in order of their ability to cause splitting Δ is called spectrochemical series. Ligands which cause large splitting (large Δ ) are called strong field ligands while those which cause small splitting (small Δ) are called weak field ligands. When strong field ligands approach metal atomlion, the value of Δ_o is large, so that electrons are forced to get paired up in lower energy t_2g orbitals. Hence, a low-spin complex is resulted from strong field ligand. When weak field ligands approach metal atom/ion, the value of Δ_o is small, so that electrons enter high energy e_g orbitals rather than pairing in low energy t_2g orbitals. Hence, a high-spin complex is resulted from weak field ligands. Strong field ligands have tendency to form inner orbital complexes by forcing the electrons to pair up. Whereas weak field ligands have tendency to form outer orbital complex because inner electrons generally do not pair up.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: In tetrahedral coordination entity formation, the d orbital splitting is inverted and is smaller as compared to the octahedral field splitting.
Reason: Spectrochemical series is based on the absorption of light by complexes with different ligands.
(ii) Assertion: F^- ion is a weak field ligand and forms outer orbital complex.
Reason: F^- ion cannot force the electrons of d_z2 and d_{x²- y²}orbitals of the inner shell to occupy d_xy, d_yz and d_zx orbitals of the same shell.
(iii) Assertion: The crystal field model is successful in explaining the formation, structures, colour and magnetic properties of coordination compounds.
Reason: In spectrochemical series, ligands are arranged in a series of increasing field strength.
(iv) Assertion: NF₃ is a weaker ligand than N(CH₃)_3.
Reason: NF₃ ionizes to give F^- ions in aqueous solution.

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Answers Key:

Generic 3

5 x 3 = 15

\(Let Rate, r=k[P]^{n} ---(i)\)
\( 8 r=k[2 P]^{n}---(ii)\\ On \ dividing \ Eq. (ii) \)
\(by \ Eq. (i), we get\)
\(\frac{8 r}{r}=\frac{k[2 P]^{n}}{k[P]^{n}}\)
\(or \ [2]^{3}=[2]^{n} \text { or } n=3\)
Therefore, order of the reaction is 3

(a) Optical isomerism is shown by the complex
[Co(en)₃]Cl₃

(b) In [Co(C₂O₄)₃]^3-, cobalt is in +3 oxidation state
Co = [Ar]3d⁷4s²
Co³⁺= 3d⁶

Magnetic character = Diamagnetic
(all electrons are paired)
(c) IUPAC name of the complex [Cr(NH₃)₃CI₃]
Triamminetrichlorochromium (III).

(iii) Manganese exhibits all the oxidation states from + 2 to + 7. It shows largest number of oxidation states as it has the maximum number of unpaired electrons.

Rate = k[NO]²[O₂].

(i) It is due to the presence of vacant d-orbitals of suitable energy, the smaller size of cautions and higher charge.
(ii) It is due to increase in effective nuclear charge gradually because unpaired electrons increase in the beginning and then decreases. There is repulsion between paired electrons.
(iii) It is due to absence of unpaired electrons, they do not absorb light from visible region and do not radiate color.

Multiple Choice Question

10 x 1 = 10

(b)
2

(d)
All of the above are true

10.

11.

12.

(b)
Ferocyanide

13.

(d)
dien

14.

15.

Generic 5

4 x 5 = 20

16.

(a) (i) It is zero order reaction
(ii) slope = - k
Negative of slope is equal to rate constant.
(b) Given if rate at 293 K is R thus 313 K rate becomes
\(4Rlog\frac{k_2}{k_1}=\frac{E_a}{2.303R}[\frac{T_2-T_1}{T_1\times T_2}]\)
\(\ log\frac{4R}{R}=\frac{E_a}{2.303\times 8.314}[\frac{313-293}{293\times313}]\)
\(\Rightarrow\ log\frac{4R}{R}=\frac{E_a}{19.1471}[\frac{20}{91709}]\)
\(\Rightarrow\ 0.6021=\frac{E_a}{19.1471}[\frac{20}{91706}]\)
\(\Rightarrow\ \ \ \ \frac{0.6021 \times 19.1471 \times 91709}{20}=E_a\)
\(\Rightarrow\ \ \ \ E_a=52863.2177\ J\ mol^{-1}\)
\(=52.863\ kJ\ mol^{-1}\)

17.

(i)The chemical formula of the compound is shown. Its name is cis-diammine dichlorido platinum (II).
(ii) It behaves as an anti cancer agent by taking part in the chelate formation or chelation.
(iii) In the trans isomer the similar groups are on opposite sides and chelate formation does not take place.
(iv) Cis-platin saves many valueable lives by forming co-ordinate complex. So it is life saving.

18.

(i) Lokesh knows about the soil pollution caused by chemical industrial waste. His responsibility towards society and environment and social awareness are displayed here.
(ii) 10FeSO₄ + 2KMn0₄ + 8H₂SO₄ \(\longrightarrow \)K₂SO₄ + 2MnSO₄ + 5 Fe₂(SO₄)₃ + 8H₂O
5H₂C₂O₄ + 2KMnO₄ + 3H₂SO₄ \(\longrightarrow \)+ K₂SO₄ + 2MnSO₄ + 8H₂O + 10CO₂

19.

(i) \([CoF_6]^{3-}\)
\( [Co(H_2O)_6]^{2+}\)
\([Co(CN)_6]^{3-}\)
(ii) \([FeF_6]^{3-}\)
\(\ [Fe(H_2O)_6]^{2+}\)
\([Fe(CN)_6]^{4-}\)
It is diamagnetic due to the absence of unpaired electrons.

Generic 2

5 x 2 = 10

20.

Coordination number 4 = [Pt(NH₃)₂ Cl₂]
Coordination number 6 = [CO(NH₃)₄ Cl₂]⁺

21.

\((i)Cr_2O_7^-(aq)+C_2O_4^{2-}(aq)+H^+(aq)⟶2Cr^{3+}+7H_2O+6CO_2\)
\((ii)MnO_4^-(aq)+Fe^{2+}(aq)+H^+(aq)⟶Mn^{2+}+4H_2O+5Fe^{3+}\)

22.

Europium (II) has electronic configuration [Xe] 4f 5do while cerium (II) has electronic configuration [Xe] 4f 5d1. In Eu²⁺, 4f - subshell is half filled and 5d-subshell is empty. Since half filled and completely filled electronic configurations are more stable, the Eu²⁺ ion is more stable than Ce²⁺in which neither 4f subshell nor 5d-subshell is half filled or completely filled.

23.

NH₃ contains a lone pair of electrons which coordinate with the metal ion to form the complex compound. However, in NH₄⁺ion, the lone pair is bound to H⁺and therefore, is not available for bonding to metal ion. Therefore, NH₄⁺ does not form complexes readily.

24.

Assertion and reason

2 x 1 = 2

25.

a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.

26.

(a): Zinc has no action of air or water on it and thus, its coating on iron articles increase their life by protecting them from rusting.

Case Study Questions

2 x 4 = 8

27.

1.(c) 3
2.(b) r = k[NO]2[Cl2]
3.(d) 3
4.(c) 177.77 M–2 min–1
5.(d) 2.77 M min–1

28.

(i) (b)
(ii) (a)
(iii) (b)
(iv) (c): Due to high electronegativity of F^-atoms, the lone pair of N^-atom in NF₃ molecule cannot be ligated easily. Whereas in N(CH₃)_3'CH₃ group is a electron releasing group, thus lone pair of N-atom in N(CH3)3 molecule can be ligated easily.

Except, nitrogen fluoride, all other halides hydrolyse in water.