Question Set E

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

For the reaction A + 2B \(\rightarrow\) C + D. The order of the reaction is

(a)

1 with respect to A

(b)

2 with respect to B

(c)

can't be predicted as order is determined experimentally.

(d)

Consider Fig. and mark the correct option.

(a)

Activation energy of forward reaction is E₁ + E₂ and product is less stable than reactant.

(b)

Activation energy of forward reaction is E₁ + E₂ and product is more stable than reactant.

(c)

Activation energy of both forward and backward reaction is E₁ + E₂ and reactant is more stable than product.

(d)

Activation energy of backward reaction is E₁and product is more stable than reactant.

In the first order reaction the concentration of reactant decreases from 0.6 M to 0.3 M in 30 minutes. The time taken for the concentration to change from 0.1 M to 0.025 M:

(a)

60 min

(b)

30 min

(c)

15 min

(d)

50 min

The product formed during Hell - Volhard - Zelinsky reaction is

(a)

(b)

(c)

(d)

Select the acid(s) which cannot be prepared by Grignard reagent?

(a)

Acetic acid

(b)

Succinic acid

(c)

Formic acid

(d)

All of these

Select the reagent for the given conversion.
\(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{8} \mathrm{CH}_{2} \mathrm{OH} \longrightarrow \mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{8} \mathrm{COOH}\)

(a)

KMnO₄ in acidic,neutral, alkaline media

(b)

K₂Cr₂O₇in acidic media

(c)

CrO₃ in acidic media

(d)

All of the above

For a hypothetical reaction, R ⟶products; rate = -k[R]. The negative sign used in the rate expression indicates.

(a)

decrease in the concentration of reactants with time

(b)

decrease in the rate with time

(c)

reaction is reversible

(d)

None of the above

Find the order of the reaction whose rate constant is 2.5 x 10^-2 min^-1

(a)

zero

(b)

three

(c)

two

(d)

one

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

10.

The correct order of increasing acidic strength is ________________.

(a)

Phenol

(b)

Ethanol

(c)

Ethanol

(d)

Chloroacetic acid

11.

A liquid was mixed with ethanol and a drop of concentrated H₂SO₄ was added. A compound with a fruity smell was formed. The liquid was

(a)

HCHO

(b)

CH₃COCH₃

(c)

CH₃COOH

(d)

CH₃OH

12.

Which of the following presents the correct order of the activity in the given compounds?

(a)

FCH₂COOH > CICH₂COOH > BrCH₂COOH > CH₃COOH

(b)

CH₃COOH > BrCH₂COOH > CICH₂COOH > FCH₂COOH

(c)

FCH₂COOH > CICH₂COOH > BrCH₂COOH > CICH₂COOH

(d)

BrCH₂COOH > CICH₂COOH > FCH₂COOH > CH₃COOH

13.

Phenol \(\xrightarrow [ dust ]{ Zn } X\xrightarrow [ Anhyd.AI{ CI }_{ 3 } ]{ { CH }_{ 3 }CI } Y\xrightarrow [ KM{ nO }_{ 4 } ]{ Alk. } Z,\) The product Z is

(a)

benzaldehyde

(b)

benzoic acid

(c)

benzene

(d)

toluene

14.

If the enolate ion combines with the carbonyl group of an ester, we get

(a)

aldol

(b)

\(\alpha ,\beta\) - unstaurated ester

(c)

\(\beta\) - ketoaldehyde

(d)

acid

15.

A compound of molecular formula CH 100% (A) reacts with Tollens' reagent to give silver mirror but does not undergo aldol condensation. The compound A is

(a)

3-pentanone

(b)

2,2-dimethylpropanal

(c)

3-hydroxy-2-pentene

(d)

3-methyllbutanone

16.

By which one of the following reactions ketones cannot prepared ?

(a)

Hydration of alkynes

(b)

Hydrolysis of gem-dihalides

(c)

Dry distillation of calcium carboxylates

(d)

Stephen's reaction

(e)

Ozonolysis of appropriately substituted alkenes

17.

The compound that does not undergo Cannizzaro reaction is

(a)

formaldehyde

(b)

acetaldehyde

(c)

benzaldehyde

(d)

trimethylacetaldehyde

18.

H2O2 is formed in the upper atmosphere through the following mechanism
H2O + (O) \(\longrightarrow\) 2OH \(\longrightarrow\) H₂O₂
The overall enthalpy change and activation energy for the forward reaction are 72 kJ mol^-1and 77 kJ mol^-1respectively. The activation energy for the decomposition of H₂O₂ to give back H₂O and (O) will be

(a)

5 kJ mol^-1

(b)

-5 kJ mol^-1

(c)

149 kJ mol^-1

(d)

-149 kJ mol^-1

19.

Which of the following statements are applicable to a balanced chemical equation of an elementary reaction ?

(a)

Order is same as molecularity

(b)

Order is less than the molecularity

(c)

Order is grater than the molecularity

(d)

Molecularity can never be zero.

20.

The rate constant, the activation energy and the Arrchenius parameter of a chemical reaction at 25^oC are 3.0 \(\times\) 10 ^-4s^-1,104.4 kJ mol^-1, and 6.0 \(\times\) 10¹⁴s^-1 respectively. The value of the rate constant as T \(\longrightarrow\) \(\infty \) is

(a)

2.0 \(\times 10^{18} s^{-1}\)

(b)

6.0 \(\times 10^{14} s^{-1}\)

(c)

Infinity

(d)

3.6\(\times 10^{30} s^{-1}\)

Assertion and reason

20 x 1 = 20

21.

Assertion: Vision is not a photochemical reaction.
Reason: Halogenation of alkenes is a photochemical 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.

22.

Assertion: Aldol condensation can be catalyzed both by acids and bases.
Reason: b-Hydroxy aldehydes or ketones readily undergo acid-catalyzed dehydration.
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

23.

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

24.

Assertion: Aldehydes undergo aldol condensation only if it has α-hydrogen.
Reason: The ∝-hydrogen in aldehydes are acidic in nature because the anion formed by the loss of the ∝-hydrogen is resonance stabilized.
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: Benzaldehyde resists nucleophilic addition in comparison with Ethanal
Reason: The Phenyl group in benzaldehyde is too bulky and therefore prevents the attack of Nucleophile.
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: Chloroacetic acid has a higher pKa value than Acetic acid.
Reason: The – I effect of Cl further stabilizes the carboxylate anion formed by the loss of the proton.
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 : 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.

28.

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.

29.

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.

30.

Assertion: Aromatic aldehydes and formaldehyde undergo Cannizzaro reaction.
Reason: Aromatic aldehydes are almost as reactive as formaldehyde.
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: \(\alpha\)-Hydrogen atoms in aldehydes and ketones are acidic.
Reason: The anion left after the removal of a-hydrogen is stabilised by inductive effect.
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: Benzaldehyde undergoes aldol condensation.
Reason: Aldehydes having a- hydrogen atom undergo aldol condensation.
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: m-Chlorobenzoic acid is a stronger acid than p-chlorobenzoic acid.
Reason: In m-chlorobenzoic acid both - I-effect and +R-effect of CI operate but in p-chlorobenzoic acid only +R-effect of Cl operates.
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: Boiling point of aldehydes lie in between parent alkanes and corresponding alcohols.
Reason: Aldehydes cannot form intermolecular hydrogen bonds like alcohols.
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: Cross aldol condensation of ethanal and prop anal gives a mixture of four products.
Reason: Ethanal and propanal, both contain a-hydrogen atom.
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 : Rate of reaction can be expressed as rate of change in partial pressure of the gaseous reactants or products.
Reason : Partial pressure of a gas is equal to its concentration.
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) Carboxylic acids have higher boiling liquids than aldehydes, ketones and even alcohols of comparable molecular masses.
Reason (R) More extensive association of carboxylic acid molecules through intermolecular hydrogen bonding is responsible for the high boiling point of carboxylic acid.
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) \(\alpha\)-hydrogen atoms of carbonyl compounds are acidic.
Reason (R) The strong electron releasing effect of the carbonyl group make the stabilisation of the conjugate base by the resonance.
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) 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.

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) Decomposition of gaseous ammonia on a hot platinum surface is a zero order reaction at high pressure.
Reason (R) At high pressure, the metal surface gets saturated with gas molecules.
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)
Activation energy of forward reaction is E₁ + E₂ and product is less stable than reactant.

(a)
60 min

(d)
All of these

(d)
All of the above

(a)
decrease in the concentration of reactants with time

(d)
one

(b)
Butan - 2 - ol

10.

11.

12.

(a)
FCH₂COOH > CICH₂COOH > BrCH₂COOH > CH₃COOH

13.

(b)
benzoic acid

14.

15.

(b)
2,2-dimethylpropanal

16.

(d)
Stephen's reaction

17.

acetaldehyde contains \(\alpha \)- hydrogens and hence does not undergo aldol condensation

18.

(a)
5 kJ mol^-1

19.

(b)
Order is less than the molecularity

20.

(b) : k = A e ^-E_a/RT . As T \(\longrightarrow\) \(\infty \) , k = A = 6.0 \(\times\) 10¹⁴ s^-1

Assertion and reason

20 x 1 = 20

21.

E) If assertion is false but reason is true.
Explanation:
Vision is a fast photochemical reaction in which the compound, retinal, present in the eye undergoes isomerisation by absorbing a photon of light.

22.

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

23.

24.

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

25.

26.

(d) If the assertion is false but the reason is true.

27.

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

28.

(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).

29.

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

30.

(c): Aromatic aldehydes and formaldehyde do not contain \(\alpha\)- hydrogen and thus undergo Cannizzaro reaction. Formaldehyde is more reactive than aromatic aldehydes.

31.

(c): The anion left after the removal of \(\alpha\)-hydrogen is stabilized by resonance effect.

32.

(d): Aldehydes having a methyl or methylene group in the a-position or more correctly having atleast one hydrogen atom in the \(\alpha\)-position undergo dimerisation in presence of a base at low temperature to form \(\beta\)-hydroxy aldehydes called aldols. As benzaldehyde does not have any \(\alpha\)-hydrogen hence it does not undergoes aldol condensation.

33.

(c) : In p-chlorobenzoic acid, both +R and -1 effect operate together but in m-chlorobenzoic acid only -I effect operates. Therefore, m-chlorobenzoic acid is a stronger acid than p-chlorobenzoic acid.

34.

(b): Aldehydes have higher molecular weight than parent alkanes as well as polarity in aldehydes shows higher boiling point than parent alkanes. Aldehydes do not have any hydrogen atom attached directly to the oxygen so they cannot form hydrogen bond with each other.

35.

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

36.

(c) : For a gaseous reaction at constant T, concentration is directly proportional to the partial pressure of the species. Thus, the rate of reaction can be expressed in terms of partial pressure for gaseous reactants or products.

37.

(a) Carboxylic acids are higher boiling liquids than aldehydes, ketones and even alcohols of comparable molecular masses. This is due to more extensive association of carboxylic acid molecules through intermolecular hydrogen bonding. Hence, both (A) and (R) are correct and (R) is the correct explanation of (A).

38.

(c) The acidity of \(\alpha\)-hydrogen atoms of carbonyl compounds is due to the strong electron withdrawing effect of the carbonyl group and resonance stabilisation of the conjugate base.

Hence, (A) is correct but (R) is incorrect.

39.

(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).

40.

(a) It is a zero order reaction at high pressure.
\( 2 \mathrm{NH}_{3}(g) \frac{1130 \mathrm{~K}}{\mathrm{Pt} \text { catalyst }} \mathrm{N}_{2}(g)+3 \mathrm{H}_{2}(\mathrm{~g}) \)
\(\text { Rate }=k\left[\mathrm{NH}_{3}\right]^{0}=k\)
In this reaction, Pt acts as a catalyst the metal surface gets saturated with gas molecules at high pressure. Thus, a further change in reaction conditions does not alter the amount of ammonia on the surface of the catalyst making rate of the reaction independent of its concentration. Thus, both (A) and (R) are correct and (R) is the correct explanation of (A).