Question Set A

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

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Questions:

Multiple Choice Question

20 x 1 = 20

Williamson's synthesis of preparing dimethyl ether is a/an

(a)

S_N1 reaction

(b)

elimination reaction

(c)

S_N2 reaction

(d)

nucleophilic addition reaction

The ions of metals of Group 12 (Zn, Cd and Hg] have completely filled d-orbitals and so they

(a)

behave like semiconductors

(b)

are very high melting points

(c)

do not behave like transition metals

(d)

behave like superconductors

Which of the following cell is used in hearing aids?

(a)

Mercury cell

(b)

H₂-O₂ fuel cell

(c)

Dry cell

(d)

Ni-Cd cell

van't Hoff factor for KCl solution assuming the complete dissociation is

(a)

(b)

(c)

0.5

(d)

1.5

Identify 'C' in the following:

(a)

Water

(b)

Ethanol

(c)

Propanone

(d)

Cumene hydroperoxide

A conductivity cell containing electrodes made up of

(a)

Gold

(b)

Silver

(c)

Platinised platinum

(d)

Copper

As the atomic number of lanthanides increases, there atomic radius decreases, but exception is

(a)

Ga and Eu

(b)

Eu and Yb

(c)

Nd and Ho

(d)

Dy and Ho

Catalyst used in the oxidsation of SO₂in the manufacture of H₂SO₄is

(a)

CuCl₂

(b)

V₂O₅

(c)

MnO₂

(d)

None of these

For the reaction, Mⁿ⁺(aq) + ne^- ⇾ M(s), select the best suitable representation of Nernst equation, when the solid M is taken.

(a)

\(\begin{array}{l} E_{M^{n+} / M}=E_{M^{n+} / M}^{0}-\frac{R T}{n F} \ln \frac{[M]}{\left[M^{n+}\right]} \\ \end{array}\)

(b)

\(E_{M^{n+} / M}=E_{M^{n+} / M}^{\circ}-\frac{R T}{n F} \ln \frac{1}{\left[M^{n+}\right]} \\ \)

(c)

\(E_{M^{n+} / M}=E_{M^{n+} / M}^{0}-\frac{R T}{n F} \ln \frac{\left[M^{n+}\right]}{[M]} \\ \)

(d)

\(E_{M^{n+} / M}=E_{M^{n+} / M}^{\circ}-\frac{R T}{n F} \ln \left[M^{n+1}\right]\)

10.

Prussian blue is

(a)

\({ K }_{ 3 }[{ Fe(CN) }_{ 6 }]\)

(b)

\({ K }_{ 4 }[{ Fe(CN) }_{ 6 }]\)

(c)

\({ K\quad Fe[Fe(CN) }_{ 6 }]\)

(d)

\({ Fe }_{ 4 }[{ Fe(CN) }_{ 6 }]\)

11.

Which of the following exhibits only +3 oxidation state ?

(a)

(b)

(c)

(d)

12.

In acidic medium, H₂O₂ changes \({ Cr }_{ 2 }{ O }_{ 7 }^{ 2- }\) to CrO₅ which has two (-O-O-) bonds. Oxidation state of Cr in CrO₅ is

(a)

+ 5

(b)

+ 3

(c)

+ 6

(d)

- 10

13.

Identify Z in the sequence of reactions: CH₃CH₂CH = CH₂\(\overset{HBr/H_2O_2}\longrightarrow\) Y \(\overset{C_2H_5ONa}\longrightarrow\) Z.

(a)

CH₃-(CH₂)₃-O-CH₂CH₃

(b)

(CH₃)₂CH-O-CH₂CH₃

(c)

CH₃-(CH₂)₄-O-CH₃

(d)

CH₃CH₂-CH(CH₃)-O-CH₂CH₃

14.

Isopropyl benzene is oxidised in the presence of air to compound 'A'. When compound 'A' is treated with dilute mineral acid,the aromatic product formed is

(a)

phenol

(b)

benzene

(c)

benzaldehyde

(d)

acetophenone

(e)

toluene

15.

Cyclohexene is best prepared from cyclohexanol by which of the following reagents:

(a)

Conc.H₃PO₄

(b)

Conc.HCl/ZnCl₂

(c)

Conc.HCl

(d)

Conc.HBr

16.

Acid-catalysed hydration of alkenes except ethane leads to the formation of

(a)

primary alcohol

(b)

secondary or tertiary alcohol

(c)

mixture of primary and secondary alcohols

(d)

mixture of secondary and tertiary alcohols

17.

Aluminium displaces hydrogen from dilute HCl whereas silver does not. The e.m.f. of a cell prepared by combining Al/Al³⁺ and Ag/Ag⁺ is 2.46 V. The reduction potential of silver electrode is + 0.80 V. The reduction potential of aluminium electrode is

(a)

+ 1.66 V

(b)

- 3.26 V

(c)

3.26 V

(d)

- 1.66 V

18.

\({ E }_{ cell }^{ \circleddash }=1.1V\) for Daniell cell. Which of the following expressions are correct description of state of equilibrium in this cell?

(a)

1.1 = K_c

(b)

\(\frac { 2.303RT }{ 2F } \log { { K }_{ c } } =1.1\)

(c)

\(\log { { K }_{ c } } =\frac { 2.2 }{ 0.059 } \)

(d)

\(\log { { K }_{ c } } =1.1\)

19.

Standard electrode potential of three metals X, Y and Z are -1.2 V, + 0.5 v and - 3.0 V respectively. The reducing power of these metals will be

(a)

X > Y > Z

(b)

Y > Z > X

(c)

Y > X > Z

(d)

Z > X > Y

20.

In the electrolytic cell, flow of electrons is from

(a)

cathode to anode in the solution

(b)

cathode to anode through external supply

(c)

cathode to anode through internal supply

(d)

anode to cathode through internal supply

Assertion and reason

20 x 1 = 20

21.

Assertion: Promethium is a man-made element.
Reason: It is radioactive and has been prepared by artificial means.
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.

22.

Assertion: Pure iron is not used for making tools and machines.
Reason: Pure iron is hard.
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.

23.

Assertion: Boiling points of alcohols are higher than ethers.
Reason: They can form intennolecular hydrogen bonding.
Codes:
A) Assertion and reason both are correct and reason is correct explanation of assertion.
B) Both assertion and reason are correct statements but reason is not correct explanation of assertion.
C) Assertion is correct statement but reason is wrong statement.
D) Assertion is wrong statement but reason is correct statement.

24.

Assertion : The bond angle in alcohols is slightly less than the tetrahedral angle.
Reason : In alcohols, the oxygen of –OH group is attached to sp3 hybridized carbon atom.
Codes:
(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
(b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
(c) If the Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.

25.

Assertion: In cell, current stops flowing when Ecell = 0.
Reason: Equilibrium of the cell reaction is attained.
Codes:
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true, but reason is not the correct explanation of assertion.
(c) If assertion is true, but reason is false.
(d) If both assertion and reason are false

26.

Assertion: Molar conductivity increases with decrease in concentration of solution.
Reason: Conductivity always decreases with decrease in concentration of solution.
Codes:
(a) If both assertion and reason are true and reason is the correct explanation of assertion.
(b) If both assertion and reason are true, but reason is not the correct explanation of assertion.
(c) If assertion is true, but reason is false.
(d) If both assertion and reason are false

27.

Assertion (A) IUPAC name of the compound

Reason (R) In IUPAC nomenclature, ether is regarded as hydrocarbon derivative in which a hydrogen atom is replaced by -OR or -OAr group [where, R = alkyl group and Ar = aryl group].
(a) Both (A) and (R) are correct, (R) is the correct explanation of (A).
(b) Both (A) and (R) are correct, (R) is not the correct explanation of (A).
(c) (A) is correct; (R) is incorrect.
(d) (A) is incorrect; (R) is correct.

28.

In the following questions a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices
Assertion: Cu²⁺ iodide is not known.
Reason: Cu²⁺ oxidises 1- to iodine.
Codes:
(a) Both assertion and reason are true, and reason is the correct explanation of the assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is not true but reason is true.
(d) Both assertion and reason are false.

29.

Assertion: For measuring resistance of an ionic solution an AC source is used.
Reason: Concentration of ionic solution will change if DC source is used.
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.

30.

Assertion: 2-Butanol on heating with H₂SO₄ gives 1-butene and 2-butene.
Reason: Dehydration of 2-butanol follows Saytzeffs rule.
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.

31.

Assertion : Auric chloride (AuCI₃ ) solution cannot be stored in a vessel made of copper, iron, nickel, chromium, zinc or tin. Reason: Gold is a very precious metal.
Reason : Gold is a very precious metal.
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.

32.

Assertion : KCI, NaCl and NH₄CI cannot be used in the salt bridge of a cell containing silver.
Reason : A salt bridge contains concentrated solution of an inert electrolyte like KCl, KNO₃ , K₂ SO₄ or solidified solution of such an electrolyte in agar-agar and gelatine.
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.

33.

Assertion : If \(\lambda^{0}{ }_{\mathrm{Na}^{+}}\) and \(\lambda^{0}{ }_{\mathrm{Cl}^{-}}\) are molar limiting conductivities of the sodium and chloride ions respectively, then the limiting molar conductivity for sodium chloride is given by the equation, \(\Lambda_{\mathrm{NaCl}}^{\circ}=\lambda_{\mathrm{Na}^{+}}^{\circ}+\lambda_{\mathrm{Cl}^{-}}^{\circ}\)
Reason : This is according to Kohlrausch law of independent migration of ions.
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.

34.

Assertion : Electrolysis of an aqueous solution of KI gives I₂at the anode but that of KF gives O₂ at the anode not F₂ .
Reason : I^- ions have much higher oxidation potential than water while F^- ions have much lower oxidation potential than water.
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.

35.

Assertion: Chromium is hard but mercury is soft.
Reason: Chromium is a 3d transition element.
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

36.

Assertion: Mn²⁺ is more stable than Mn³⁺.
Reason: Mn²⁺ has half-filled configuration.
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.

37.

In the following questions. an Assertion (A) is followed by a corresponding Reason (R) Use the following keys to choose the appropriate answer.
Assertion (A) Bromination of phenol takes place even in the absence of Lewis acid.
Reason (R) In phenol, OH group attached to benzene ring has highly deactivating effect.
Codes:
(a) Both (A) and (R) are correct, (R) is the correct explanation of (A).
(b) Both (A) and (R) are correct, (R) is not the correct explanation of (A).
(c) (A) is correct; (R) is incorrect.
(d) (A) is incorrect; (R) is correct.

38.

In the following questions. an Assertion (A) is followed by a corresponding Reason (R) Use the following keys to choose the appropriate answer.
Assertion (A) Alcohols and phenols are soluble in water.
Reason (R) There occurs a dipole-dipole interaction of OH group of alcohol and phenol with water molecules which is responsible for their solubility in water.
Codes:
(a) Both (A) and (R) are correct, (R) is the correct explanation of (A).
(b) Both (A) and (R) are correct, (R) is not the correct explanation of (A).
(c) (A) is correct; (R) is incorrect.
(d) (A) is incorrect; (R) is correct.

39.

In the following questions an Assertion (A) is followed by a corresponding Reason (R) Use the following keys to choose the appropriate answer.
Assertion (A) First ionisation enthalpy of Cr is lower than that of Zn.
Reason (R) Ionisation enthalpy of Cr is lower than Zn due to the stability of d⁵ -electron configuration.
Codes:
(a) Both (A) and (R) are correct, (R) is the correct explanation of (A).
(b) Both (A) and (R) are correct, (R) is not the correct explanation of (A).
(c) (A) is correct; (R) is incorrect.
(d) (A) is incorrect; (R) is correct.

40.

In the following questions.an Assertion (A) is followed by a corresponding Reason (R) Use the following keys to choose the appropriate answer.
Assertion (A) Mercury cells give a constant voltage throughout its life.
Reason (R) Electrolyte KOH is not involved in the reaction.
Codes:
(a) Both (A) and (R) are correct, (R) is the correct explanation of (A).
(b) Both (A) and (R) are correct, (R) is not the correct explanation of (A).
(c) (A) is correct; (R) is incorrect.
(d) (A) is incorrect; (R) is correct.

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Answers Key:

Multiple Choice Question

20 x 1 = 20

(a)
Mercury cell

(b)
2

(b)
Eu and Yb

(b)
V₂O₅

(b)
\(E_{M^{n+} / M}=E_{M^{n+} / M}^{\circ}-\frac{R T}{n F} \ln \frac{1}{\left[M^{n+}\right]} \\ \)

10.

11.

(a)
Ac

12.

13.

(a)
CH₃-(CH₂)₃-O-CH₂CH₃

14.

(a)
phenol

15.

(a)
Conc.H₃PO₄

16.

(b)
secondary or tertiary alcohol

17.

(d)
- 1.66 V

18.

(b)
\(\frac { 2.303RT }{ 2F } \log { { K }_{ c } } =1.1\)

19.

(d)
Z > X > Y

20.

In an electrolytic cell, electrons enter the cathode and leave at the anode. Thus, in the external supply, electrons flow from cathode to anode. In the solution, only ions flow and not the electrons.

Assertion and reason

20 x 1 = 20

21.

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

22.

c) Assertion is not true but the reason is true.

23.

C) Assertion is correct statement but reason is wrong statement.
Explanation:
Assertion is correct. Correct reason. Intermolecular hydrogen bonding is present in alcohols but not in ethers.

24.

(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.

25.

(a) If both assertion and reason are true and reason is the correct explanation of assertion.
Explanation:
For reaction to be spontaneous, Ecell should have a positive value and Δr Gcell negative. Hence, Current stops flowing when Ecell = 0 because equilibrium of the cell reaction is attained. Thus, both assertion and reason are true and reason is the correct explanation of assertion

26.

(b) If both assertion and reason are true, but reason is not the correct explanation of assertion.
Explanation:
Conductivity always decreases with a decrease in concentration whereas, molar conductivity increase with dilution. This is because the conductivity of a solution is the conductance of one-unit volume of the solution, but molar conductivity is the conductance of that volume of solution containing one mole of an electrolyte. Thus, both assertion and reason are correct but reason is not the correct explanation of assertion.

27.

(d) (A) is incorrect statement but (R) is correct statement, Correct (A) The IUPAC name of the given compound is 1-(2-propoxy) propane.

28.

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

29.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

30.

(a): Saytzeff's rule: The alkene formed in greatest amount is the one that corresponds to removal of the hydrogen from the \(\beta\) -carbon having the fewest hydrogen substituent. In case of 2° and 3° alcohols Saytzeff's rule is followed.

31.

(b) : Gold has higher reduction potential than the given metals. Hence, AuCl₃ will react with these metals.

32.

(b) : KCI, NaCI and NH₄CI cannot be used as salt bridge in a cell containing silver as one of the electrodes because they react to form a precipitate of AgCl.

33.

(a) : According to Kohlrausch law, "limiting molar conductivity of an electrolyte can be represented as the sum of the individual contributions of the anion and cation of the electrolyte".

34.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

35.

(b): Chromium has maximum number of unpaired d electrons while Hg do not have any unpaired d electrons. Thus, Cr is hard but Hg is soft metal.

36.

(a): A half-filled or fully-filled orbital is more stable than incompletely filled orbital.

37.

(c) In case of phenol, the polarisation of bromine molecule takes place even in the absence of Lewis acid. It is due to the highly activatingeffect of OH group attached to the benzene ring. Hence, (A) is correct but (R) is incorrect.

38.

(c) Solubility of alcohols and phenols in water is due to their ability to form hydrogen bonds with water molecules.
The solubility decreases with increase in size of the alkyl/aryl groups. Several lower molecular mass alcohols are miscible with water in all proportions. Hence, (A) is correct but (R) is incorrect.

39.

(a) First ionisation enthalpy of Cr is lower than that of Zn due to the stability of d⁵ by losing one electron from outer s-orbital and the value for Zn is higher due to stable d¹⁰ s² configuration.

40.

(c) Mercury cell gives the constant voltage throughout its life because the overall reaction does not involve any ion in the solution, concentration of which changes during its whole life.Thus, (A) is correct but (R) is incorrect.