Here is a set of 50 assertion-reason questions for CBSE Class 12 Chemistry, based on Chapter 12, "Aldehydes, Ketones, and Carboxylic Acids" from the NCERT Class 12 Chemistry book.
Reason: Aldehydes have one alkyl group attached to the carbonyl
carbon, while ketones have two alkyl groups attached to the carbonyl carbon.
Answer: (C) Assertion is true, reason is false.
Explanation: The presence of two alkyl groups in ketones makes
the electron donation effect greater, making ketones less electrophilic than
aldehydes, hence less reactive towards nucleophilic addition.
Reason: The oxygen atom in the carbonyl group is more
electronegative than carbon.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The carbonyl group is polar due to the difference
in electronegativity between carbon and oxygen, resulting in a partial positive
charge on carbon and a partial negative charge on oxygen.
Reason: Ketones lack a hydrogen atom attached to the carbonyl
group, which is required for oxidation.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The absence of a hydrogen atom in ketones prevents
their oxidation to carboxylic acids, whereas aldehydes can be oxidized because
they have a hydrogen attached to the carbonyl carbon.
Reason: The conjugate base of carboxylic acid is stabilized by
resonance, while the conjugate base of alcohols is not.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The conjugate base of carboxylic acid is
stabilized by resonance, while the conjugate base of alcohol is not, making
carboxylic acids stronger acids than alcohols.
Reason: Ketones have a carbonyl group which is electrophilic in
nature and attracts nucleophiles.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The electrophilic carbonyl group in ketones
attracts nucleophiles, allowing them to undergo nucleophilic addition reactions.
Reason: Carboxylic acids form hydrogen bonds between molecules,
while aldehydes and ketones cannot.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The ability of carboxylic acids to form hydrogen
bonds with other molecules leads to higher boiling points compared to aldehydes
and ketones, which cannot form similar intermolecular forces.
Reason: Formaldehyde has no alkyl group, while acetaldehyde has
a methyl group that slightly stabilizes the carbonyl group.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The absence of an alkyl group in formaldehyde
makes its carbonyl group more electrophilic and reactive towards nucleophiles
than acetaldehyde, which has a methyl group that provides some stabilization.
Reason: The conjugate base of carboxylic acid is stabilized by
resonance, while the conjugate base of phenols is not.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The resonance stabilization of the conjugate base
of carboxylic acids makes them more acidic compared to phenols, where the
conjugate base is less stabilized.
Reason: Aldehydes have only one alkyl group attached to the
carbonyl carbon, making the carbonyl carbon more electrophilic.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The single alkyl group in aldehydes does not
provide much electron donation, making the carbonyl carbon more electrophilic
and thus more reactive towards nucleophiles compared to ketones, which have two
alkyl groups.
Reason: Electronegative substituents stabilize the negative
charge on the conjugate base through inductive or resonance effects.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Electronegative substituents such as halogens can
withdraw electron density, stabilizing the negative charge on the conjugate base
of carboxylic acid, which increases its acidity.
Reason: Ketones have two alkyl groups attached to the carbonyl
carbon, which donate electron density and make the carbonyl carbon less
electrophilic.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The electron-donating effect of two alkyl groups
in ketones makes the carbonyl carbon less electrophilic, thus slowing down
nucleophilic addition reactions compared to aldehydes.
Reason: Aldehydes have a hydrogen atom attached to the carbonyl
group, which facilitates oxidation.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The hydrogen attached to the carbonyl carbon in
aldehydes makes them more susceptible to oxidation, leading to the formation of
carboxylic acids.
Reason: The presence of two alkyl groups in ketones provides
more electron density to the carbonyl carbon, reducing its electrophilicity.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The electron-donating effect of the two alkyl
groups in ketones reduces the electrophilic character of the carbonyl carbon,
making ketones less reactive towards nucleophilic addition than aldehydes.
Reason: Electron-withdrawing groups stabilize the conjugate
base of carboxylic acid, making it more acidic.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Electron-withdrawing groups like nitro or halogen
groups stabilize the negative charge on the conjugate base through inductive and
resonance effects, increasing the acidity of carboxylic acids.
Reason: Carboxylic acids form hydrogen bonds, whereas aldehydes
and ketones do not.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The hydrogen bonding between carboxylic acid
molecules increases their boiling points compared to aldehydes and ketones,
which lack such intermolecular forces.
Reason: Esters have a negative inductive effect due to the
alkoxy group, reducing the electrophilicity of the carbonyl carbon.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The alkoxy group in esters has a negative
inductive effect, reducing the electron deficiency of the carbonyl carbon and
making it less reactive towards nucleophilic addition compared to aldehydes.
Reason: The carbonyl carbon has a partial positive charge,
making it susceptible to nucleophilic attack.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The partial positive charge on the carbonyl carbon
makes it electrophilic and prone to nucleophilic attack, leading to the
formation of a tetrahedral intermediate.
Reason: The reaction between carboxylic acids and alcohols is
an esterification reaction.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The reaction between carboxylic acids and
alcohols, known as esterification, forms an ester and is catalyzed by an acid.
Reason: Acetic acid molecules are capable of forming hydrogen
bonds, while ethanol molecules can only form intermolecular hydrogen bonds.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Acetic acid molecules can form strong hydrogen
bonds with each other, leading to a higher boiling point compared to ethanol,
which also forms hydrogen bonds but not as strongly as acetic acid.
Reason: The alkyl groups in esters donate electron density
through induction, reducing the electrophilicity of the carbonyl carbon.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The alkyl groups in esters donate electron density
to the carbonyl group, making it less electrophilic than the carbonyl group in
aldehydes and ketones.
Reason: Aldehydes have a hydrogen atom attached to the carbonyl
group, while ketones have two alkyl groups.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The presence of a hydrogen atom in aldehydes
allows their reduction to primary alcohols, whereas ketones, with two alkyl
groups, are reduced to secondary alcohols.
Reason: The presence of two alkyl groups in ketones increases
the electron density on the carbonyl carbon, making it less electrophilic.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The two alkyl groups in ketones donate electron
density, reducing the electrophilicity of the carbonyl carbon and making ketones
less reactive towards nucleophilic addition than aldehydes.
Reason: The conjugate base of carboxylic acid is stabilized by
resonance, whereas the conjugate base of phenol is less stabilized.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The conjugate base of carboxylic acid is more
stabilized by resonance than the conjugate base of phenol, making carboxylic
acids stronger acids.
Reason: Esters can be hydrolyzed back to carboxylic acids and
alcohols in the presence of an acid or base catalyst.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The esterification reaction, which forms esters
from carboxylic acids and alcohols, is reversible and can be hydrolyzed in the
presence of an acid or base catalyst to regenerate the carboxylic acid and
alcohol.
Reason: Aldehydes and ketones can form dipole-dipole
interactions but cannot form hydrogen bonds like alcohols and carboxylic acids.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The ability of aldehydes and ketones to form
dipole-dipole interactions increases their boiling point compared to
hydrocarbons, but they do not form hydrogen bonds, which results in lower
boiling points than alcohols and carboxylic acids.
Reason: Aldehydes have only one alkyl group attached to the
carbonyl carbon, making the carbonyl carbon more electrophilic.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The electrophilic carbonyl carbon in aldehydes,
due to the presence of only one alkyl group, is more susceptible to nucleophilic
attack, making aldehydes more reactive than ketones.
Reason: The hydrogen atom in aldehydes does not donate electron
density to the carbonyl carbon, unlike alkyl groups in ketones.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The lack of electron-donating groups in aldehydes
makes the carbonyl carbon more electrophilic and polarized compared to ketones,
which have alkyl groups that donate electron density.
Reason: Electron-withdrawing groups stabilize the negative
charge on the conjugate base of carboxylic acid.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Electron-withdrawing groups, such as halogens,
stabilize the conjugate base of carboxylic acids through inductive and resonance
effects, thereby increasing their acidity.
Reason: Ketones have two alkyl groups attached to the carbonyl
carbon, which make the carbonyl carbon less electrophilic.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The two alkyl groups in ketones donate electron
density to the carbonyl carbon, reducing its electrophilicity and making ketones
less reactive than aldehydes in nucleophilic addition reactions.
Reason: Ketones have two alkyl groups attached to the carbonyl
carbon, which are reduced to a secondary alcohol upon addition of hydrogen.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The reduction of ketones involves the addition of
hydrogen to the carbonyl group, producing secondary alcohols because ketones
have two alkyl groups attached to the carbonyl carbon.
Reason: Carboxylic acids form hydrogen bonds, while aldehydes
and ketones cannot form such bonds.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The ability of carboxylic acids to form hydrogen
bonds increases their boiling points and decreases their volatility compared to
aldehydes and ketones, which cannot form such strong intermolecular forces.
Reason: Carboxylate ions are stabilized by resonance, whereas
alkoxide ions are not.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The conjugate base of carboxylic acid is
stabilized by resonance, whereas alcohols do not have such stabilization for
their conjugate bases, making carboxylic acids stronger acids.
Reason: Aldehydes have a hydrogen atom attached to the carbonyl
group, which makes them more easily oxidized.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The hydrogen atom in aldehydes makes them more
easily oxidized to carboxylic acids compared to ketones, which lack a hydrogen
atom attached to the carbonyl carbon.
Reason: The reduction of ketones involves the addition of
hydrogen to the carbonyl group.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Ketones undergo reduction by adding hydrogen to
the carbonyl group, leading to the formation of secondary alcohols.
Reason: Aldehydes possess a nucleophilic carbonyl carbon, which
easily reacts with the nucleophilic bisulfite ion.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Aldehydes undergo nucleophilic addition with
bisulfite ions, resulting in the formation of a bisulfite addition product due
to the electrophilic nature of the carbonyl carbon.
Reason: Aldehydes have only one alkyl group attached to the
carbonyl carbon, making the carbonyl carbon more electrophilic.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The electrophilic nature of aldehydes, due to the
presence of only one alkyl group, makes the carbonyl carbon more prone to
nucleophilic attack compared to ketones, which have two alkyl groups.
Reason: Aldehydes have a hydrogen atom attached to the carbonyl
group, making them more easily reducible to alcohols.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The hydrogen atom in aldehydes makes them more
easily reducible to primary alcohols upon the addition of hydrogen.
Reason: Carboxylic acids can undergo reduction by
hydrogenation, which adds hydrogen to the carbonyl group, forming alcohols.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Carboxylic acids can be reduced by hydrogenation,
which adds hydrogen to the carbonyl group, converting the carboxyl group (-COOH)
to a hydroxyl group (-OH), thus forming alcohols.
Reason: The carbonyl carbon in carboxylic acids is
electrophilic and reacts with nucleophilic alcohols to form esters.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The electrophilic carbonyl carbon in carboxylic
acids is attacked by the nucleophilic alcohol group in a nucleophilic acyl
substitution reaction, resulting in the formation of esters.
Reason: Aldehydes undergo halogenation at the α-carbon in the
presence of bromine, resulting in halogenated products.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Aldehydes undergo halogenation at the α-carbon in
the presence of bromine, resulting in the formation of α,β,γ-tri-bromo
aldehydes.
Reason: Grignard reagents act as nucleophiles, attacking the
electrophilic carbonyl carbon of aldehydes and ketones.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Grignard reagents are strong nucleophiles that
attack the electrophilic carbonyl carbon in aldehydes and ketones, leading to
the formation of alcohols after hydrolysis.
Reason: Aldehydes have a hydrogen atom attached to the carbonyl
group, which is easily oxidized to a carboxyl group.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The hydrogen atom attached to the carbonyl carbon
in aldehydes makes them more susceptible to oxidation, converting them into
carboxylic acids.
Reason: Ketones do not have a hydrogen atom attached to the
carbonyl group, making them less susceptible to oxidation.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Unlike aldehydes, ketones lack a hydrogen atom
attached to the carbonyl carbon, which makes them resistant to oxidation.
Reason: This reaction, known as esterification, involves
nucleophilic attack by the alcohol on the carbonyl carbon of the carboxylic
acid.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: In the esterification reaction, the alcohol acts
as a nucleophile, attacking the electrophilic carbonyl carbon of the carboxylic
acid, resulting in the formation of esters.
Reason: Sodium borohydride is a mild reducing agent that can
reduce aldehydes without affecting other functional groups.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Sodium borohydride is a selective reducing agent
that reduces aldehydes to primary alcohols, but it does not reduce other
functional groups such as esters or carboxylic acids under mild conditions.
Reason: The nitrogen atom in ammonia or its derivatives acts as
a nucleophile, attacking the carbonyl carbon in aldehydes to form imines.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Ammonia and its derivatives are nucleophilic and
attack the electrophilic carbonyl carbon of aldehydes, leading to the formation
of imines.
Reason: Ketones contain two alkyl groups attached to the
carbonyl carbon, which are reduced to a secondary alcohol during the reaction.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Lithium aluminum hydride reduces ketones to
secondary alcohols by adding hydrogen to the carbonyl carbon, where both alkyl
groups remain attached.
Reason: Carboxylic acids form strong hydrogen bonds between
molecules, resulting in high boiling points compared to aldehydes and ketones.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Carboxylic acids form strong hydrogen bonds, which
significantly raise their boiling points compared to aldehydes and ketones,
which do not form such strong intermolecular interactions.
Reason: Ketones have two alkyl groups attached to the carbonyl
carbon, providing greater electron density and stabilizing the carbonyl group.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: The two alkyl groups in ketones donate electron
density to the carbonyl carbon, making it more stable compared to aldehydes,
which have only one alkyl group.
Reason: Soda lime (a mixture of NaOH and CaO) induces the
removal of the carboxyl group (-COOH) from carboxylic acids, forming an alkane.
Answer: (A) Assertion is true, reason is true, and reason is
the correct explanation for assertion.
Explanation: Heating carboxylic acids with soda lime causes
decarboxylation, where the carboxyl group is removed, resulting in the formation
of an alkane.