Question Set C

cbse 12th Standard Chemistry Aldehydes , Ketones and Carboxylic Acids Important Questions And Answers Study Material - QB365

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Questions:

Multiple Choice Question

20 x 1 = 20

Compounds A and C in the following reaction are

(a)

identical

(b)

positional isomers

(c)

functional isomers

(d)

optical isomers

In Arrhenius plot of Ink Vs \(\frac{1}{\mathrm{~T}}\) is a linear plot obtained with slope of -2 x 10⁴ k. Ea of reaction in kJ mol ^-1.

(a)

(b)

166

(c)

249

(d)

332 kJ mol ^-1

Which of the following is affected by catalyst?

(a)

\(\triangle\)H

(b)

\(\triangle\)S

(c)

\(\triangle\)G

(d)

E_a

Ethyne + H₂O Product formed in the given reaction is

(a)

benzaldehyde

(b)

acetaldehyde

(c)

ethanoic acid

(d)

ethanoyl chloride

Which of the following compounds is most reactive towards nucleophilic addition reactions?

(a)

(b)

(c)

(d)

Addition of water to butyne occurs in acidic medium and in the presence of Hg²⁺ ions as a catalyst. The product formed is

(a)

(b)

(c)

(d)

Which of the following compounds will give butanone on oxidation with alkaline KMnO₄ solution?

(a)

Butan - I - oI

(b)

Butan - 2 - ol

(c)

Both of these

(d)

None of these

Which of the following reagents are used for detecting the presence of carbonyl group ?

(a)

NH₂OH

(b)

NH₂NH₂

(c)

H₂NCONHNH₂.HCI

(d)

C₆H₅NHNH₂.HCI

The distinguishing test between methanoic acid and ethanoic acid is

(a)

Tollens' test

(b)

sodium bicarbonate test

(c)

Litmus test

(d)

esterification test

10.

When CH₂ = CH ^_COOH is reduced with LiAIH₄ the compound obtained will be

(a)

CH₃^_CH₂^_CHO

(b)

CH₃^_CH₂^_COOH

(c)

CH₂=CH ^_CH₂OH

(d)

CH₃^_CH₂^_COOH

11.

Methyl benzoate can ve prepared by

(a)

C₆H₅COOH + CH₃OH \(\xrightarrow {H^{+}}\)

(b)

C₆H₅COCI+ CH₃OH \(\xrightarrow {Pyridine}\)

(c)

C₆H₅COOH + CH₃N₂ \(\longrightarrow \)

(d)

All the above methods

12.

Sodium ethoxide reacts with ethanoyl chloride. The compound that is produced in the above reaction is

(a)

2-butanone

(b)

ethyl chloride

(c)

ethyl ethanoate

(d)

diethyl ether

13.

The correct increasing order of the acid strength of benzoic acid (I), 4-nitrobenzoic acid (II),3, 4-finitrobenzonic acid (III) and 4-methoxybenzoic acid (IV) is

(a)

I < II < III < IV

(b)

II < I < IV < III

(c)

IV < I < II < III

(d)

IV < II < I < III

(e)

I < IV < II < III

14.

Which of the following is the industrial method of preparation of acetaldeyde ?

(a)

CH3CN \(\xrightarrow [ HCI ]{ Sn{ CI }_{ 2 } } \) CH3CH = NH \(\xrightarrow {H_3O^{+}}\)

(b)

CH3COCI + H2 \(\xrightarrow [ BaSO_4 ]{Pd } \) CH3CHO + HCI

(c)

CH2 = CH2 + H2O \(\xrightarrow {Pd ^{2+}}\)

(d)

All of the above.

15.

Kinetics of the reaction A (g) \(\longrightarrow\) 2 B (g) + C (g) is followed by measuring the total pressure at different times. It is given that
Initial pressure of A = 0.5 atm.
Total pressure of A after 2 hours = 0.7 atm
Rate constant of the reaction = 1 \(\times 10 ^{-3}s^{-1}\)
What is the rate of reaction \(-\frac {d[A]}{dt}\) when the total pressure is 0.7 atm?

(a)

2.0 \(\times 10^{-4}M s^{-1}\)

(b)

4.0\(\times 10^{-4}M s^{-1}\)

(c)

5.0\(\times 10^{-4}M s^{-1}\)

(d)

7.0\(\times 10^{-4}M s^{-1}\)

16.

According to Maxwell Boltzmann distribution of energy, ....... .

(a)

the fraction of molecules with most probable kinetic energy decreases at higher temperatures

(b)

the fraction of molecules with most probable kinetic energy increases at higher temperatures

(c)

most probable kinetic energyincreases at higher temperatures

(d)

most probable kinetic energy decreasesat higher temperatures.

17.

75% of the first order reaction was completed in 32 min. 50% of the reaction was completed in

(a)

24 min

(b)

8 min

(c)

16 min

(d)

4 min

18.

The rate of a chemical reaction doubles for every 10^oC rise of temperature. If the temperature is raised by 50^oC, the rate the reaction increses by about :

(a)

24 times

(b)

32 times

(c)

64 times

(d)

10 times

19.

A first order reaction has a half-life period of 34.65 seconds. Its rate constant is

(a)

2 \(\times 10\) ^-2 sec^-1

(b)

4 \(\times 10\) ^-4 sec^-1

(c)

20 sec^-1

(d)

2 \(\times 10\) ^-4 sec^-1

20.

In a reaction \(\longrightarrow\) B, the rate of reaction increases two times on increasing the concentration of the reactant four times, then order of reaction is

(a)

(b)

(c)

1/2

(d)

Assertion and reason

20 x 1 = 20

21.

Assertion: Glow worm shows chemiluminescence.
Reason: Glow worm emits light due to oxidation of protein, luciferin present in it.
Codes:
A) If both assertion and reason are true and the reason is the correct explanation of the assertion.
B) If both assertion and reason are true but reason is not the correct explanation of the assertion.
C) If assertion is true but reason is false.
D) If the assertion and reason both are false.
E) If assertion is false but reason is true.

22.

Assertion: According to steady state hypothesis, in a multistep reaction, the change in concentration with time for reactive intermediates is zero.
Reason: The intermediates are so reactive that after a brief initial period their concentrations rise from zero to a small value and remains constant for most of the duration of the reaction.
Codes:
A) If both assertion and reason are true and the reason is the correct explanation of the assertion.
B) If both assertion and reason are true but reason is not the correct explanation of the assertion.
C) If assertion is true but reason is false.
D) If the assertion and reason both are false.
E) If assertion is false but reason is true.

23.

Assertion: a-Hydrogen atoms in aldehydes and ketones are acidic.
Reason: The anion left after the removal of a-hydrogen is stabilized by the inductive effect.
Codes:
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but the reason is not the correct explanation of the assertion.
(c) If the assertion is true but the reason is false.
(d) If the assertion is false but the reason is true.
(e) If the assertion and reason both are false

24.

Assertion: Formaldehyde cannot be prepared by Rosenmund’s reduction.
Reason: Acid chlorides can be reduced into aldehydes with hydrogen in boiling xylene using palladium or platinum as a catalyst supported on barium sulphate. This is known as Rosenmund’s reduction.
Codes:
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but the reason is not the correct explanation of the assertion.
(c) If the assertion is true but the reason is false.
(d) If the assertion is false but the reason is true.
(e) If the assertion and reason both are false

25.

Assertion: Ketones have a low boiling point compared to corresponding alcohols.
Reason: Ketones from intermolecular hydrogen bonding with alcohols.
Codes:
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but the reason is not the correct explanation of the assertion.
(c) If the assertion is true but the reason is false.
(d) If the assertion is false but the reason is true.
(e) If the assertion and reason both are false

26.

Assertion: Isobutanal does not give an iodoform test.
Reason: It does not have ∝-hydrogen.
Codes:
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but the reason is not the correct explanation of the assertion.
(c) If the assertion is true but the reason is false.
(d) If the assertion is false but the reason is true.
(e) If the assertion and reason both are false

27.

Assertion: Acetaldehyde on treatment with alkaline gives aldol.
Reason: Acetaldehyde molecules contain a hydrogen atom.
Codes:
(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) If both assertion and reason are true but the reason is not the correct explanation of the assertion.
(c) If the assertion is true but the reason is false.
(d) If the assertion is false but the reason is true.
(e) If the assertion and reason both are false

28.

Assertion : The boiling points of aldehydes and ketones are higher than hydrocarbons and ethers of comparable molecular masses.
Reason : There is a weak molecular association in aldehydes and ketones arising out of the dipole-dipole interactions.
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.

29.

Assertion (A) : Hydrolysis of an ester follows first order kinetics.
Reason (R) : Concentration of water remains nearly constant during the course of the reaction.
(a) Both Assertion and Reason are correct, Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are correct, Reason is not the correct explanation of Assertion.
(c) Assertion is correct; Reason is incorrect.
(d) Assertion is incorrect; Reason is correct.

30.

Assertion (A) Aromatic carboxylic groups do not undergo Friedel- Crafts reaction.
Reason (R) Carboxyl group is deactivating and the catalyst aluminium chloride gets bonded to the carboxyl group.
(a) Both (A) and (R) are correct and (R) is the correct explanation of (A).
(b) Both (A) and (R) are correct but (R) is not the correct explanation of (A).
(c) (A) is correct but (R) is incorrect.
(d) (A) is incorrect but (R) is correct.

31.

Assertion (A) p-methoxyphenol is a stronger acid than m-methoxyphenol. Reason (R) Methoxy group exerts + R effect at both ortho and para position.
(a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
(c) Assertion (A) is true, but Reason (R) is false.
(d) Assertion (A) is false, but Reason (R) is true.

32.

In the following questions a statement of assertion followed by a statement of reason is given.
Assertion: All collision of reactant molecules lead to product formation.
Reason: Only those collisions in which molecules have correct orientation and sufficient kinetic energy lead to compound formation .
Codes:
(a) Both assertion and reason are correct and the reason is correct explanation of assertion.
(b) Both assertion and reason are correct but reason does not explain assertion.
(c) Assertion is correct but reason is incorrect,
(d) Both assertion and reason are incorrect.
(e) Assertion is incorrect but reason is correct.

33.

Assertion: During reaction of carboxylic acids with NaHCO₃, the CO₂evolved comes from carboxylic acid and not from NaHCO₃.
Reason: Carbonic acid is a weaker acid than carboxylic acid.
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: Acetic acid in vapour state shows a molecular mass of 120.
Reason: It undergoes intermolecular hydrogen bonding.
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: Lower aldehydes and ketones are soluble in water but the solubility decreases as the molecular mass increases.
Reason: Distinction between aldehydes and ketones can be done by Tollens test.
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: NaHSO₃ is used for the purification of carbonyl compounds.
Reason: They are used in the blending of perfumes and flavouring agents.
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.

Assertion : The decomposition of NH3 on finely divided platinum surface is first order when the concentration is low, however at higher concentration, the reaction becomes zero order.
Reason : In first order reaction, the rate of reaction is proportional to the first power of the concentration of the reactant
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.

38.

Assertion : The rate of the reaction is the rate of change of concentration of a reactant or a product.
Reason : Rate of reaction remains constant during the complete reaction.
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.

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) Order of reaction can be zero or fractional.
Reason (R) We cannot determine order from balanced chemical equation.
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) A positive catalyst increases the rate of reaction.
Reason (R) A catalyst increases the rate of reaction by making available a new and more efficient mechanism.
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

(b)
positional isomers

(b)
166

(d)
E_a

(b)
acetaldehyde

(b)
Butan - 2 - ol

(a)
Tollens' test

10.

11.

(d)
All the above methods

12.

13.

14.

15.

(b)
4.0\(\times 10^{-4}M s^{-1}\)

16.

(a)
the fraction of molecules with most probable kinetic energy decreases at higher temperatures

17.

18.

(b)
32 times

19.

(a) : \(k = \frac {0.693}{t/2}= \frac {0.693}{34.65}s^{-1} = 2 \times 10^{-2}\)s^-1

20.

(c) : (i) r = k \(a ^ { \alpha}\) (ii) 2 r = k (4 a) ^{^\(\alpha\)}dividing (ii) by (i), 4^{^\(\alpha\)}= 2 or 2 \(\alpha\)= 1/2

Assertion and reason

20 x 1 = 20

21.

A) If both assertion and reason are true and the reason is the correct explanation of the assertion.
Explanation:
The emission of cold light during a chemical reaction is called chemiluminescence.

22.

A) If both assertion and reason are true and the reason is the correct explanation of the assertion.

23.

24.

(b) If both assertion and reason are true but the reason is not the correct explanation of the assertion.

25.

(b) If both assertion and reason are true but the reason is not the correct explanation of the assertion.

26.

27.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

28.

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

29.

(a) (a) Both Assertion and Reason are correct, Reason is the correct explanation of Assertion.
Consider the hydrolysis of an ester
\( \mathrm{CH}_3 \mathrm{COOC}_2 \mathrm{H}_5+\mathrm{H}_2 \mathrm{O} \longrightarrow \mathrm{CH}_3 \mathrm{COOH}+\mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}\)
\(\text { Rate }=k\left[\mathrm{CH}_3 \mathrm{COOC}_2 \mathrm{H}_5\right]\left[\mathrm{H}_2 \mathrm{O}\right] \)
Hydrolysis of an ester follows first order because the concentration of water, \(\left[\mathrm{H}_2 \mathrm{O}\right]\) remains nearly constant and the change in the concentration of acid will result in very negligible change in the concentration of \(\mathrm{H}^{+} / \mathrm{OH}^{-}\)ion during the course of the reaction.
Thus, both (A) and (R) are correct and (R) is the correct explanation of (A).

30.

(a) Aromatic carboxylic groups do not undergo Friedel-Crafts reaction because carboxyl group is deactivating and the catalyst aluminium chloride gets bonded to the carboxyl group.

31.

(d) Methoxy group exerts -I effect at m-position and +R effect at p-position thereby make m-methoxyphenol a stronger acid than p-methoxyphenol.
Hence, Assertion (A) is false but Reason (R) is true.

32.

(e) Assertion is incorrect but reason is correct. All collisions are never effective.

33.

(d): During reaction of carboxylic acids with NaHCO₃, CO₂ evolved comes from NaHCO₃. Carboxylic acid is a stronger acid than carbonic acid.

34.

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

35.

(b): Lower aldehydes and ketones are soluble in water due to polar effect of C = O group which makes hydrogen bonds with water molecules. As the size of the aldehydes and ketones increases the hydrophobic part i.e., alkyl chain increases which weakens the H-bond formations with H₂O molecules and decreases the solubility.

36.

(b): Carbonyl compounds form solid additive products with NaHSO₃ which are separated out. The solid bisulphites of carbonyl compounds on hydrolysis with dilute acid regenerate original carbonyl compounds and thus, this property is used for the purification of carbonyl compounds as well as for their separation.

37.

(b) : In a heterogeneous system, the reactant is absorbed on the surface of a solid catalyst. The fraction of the surface of the catalyst covered by the reactant is proportional to its concentration at low values and the rate of reaction is first order. However at higher concentration, the surface of catalyst is fully covered and the reaction rate becomes independent of concentration and it becomes zero order reaction.

38.

(c) : Rate of reaction does not remain constant during the complete reaction because rate depends upon the concentration of reactants which decreases with time

39.

(b) Order of reaction can be zero or fractional as order of reaction is directly related to sum of power of reactants. Hence, both (A) and (R) are correct and (R) is the correct explanation of (A).

40.

(a) A positive catalyst increases rate of reaction by making a new and more efficient mechanism. Thus, both (A) and (R) are correct and (R) is the correct explanation of (A).