Test: Aldehydes, Ketones And Carboxylic Acids 3 - From Past 28 Years Questions


25 Questions MCQ Test Chemistry 28 Years Past year papers for NEET/AIPMT Class 12 | Test: Aldehydes, Ketones And Carboxylic Acids 3 - From Past 28 Years Questions


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QUESTION: 1

If formaldehyde and KOH are heated, then we get  [1988]

Solution:

Aldehydes containing no α-hydrogen atom on warming with 50% NaOH or KOH undergo disproportionation i.e. self oxidation -reduction known as Cannizzaro’s reaction

QUESTION: 2

Formalin is an aqueous solution of    [1988]

Solution:

Formalin is an aqueous solution (40%) of formaldehyde.

QUESTION: 3

Which of the following is the correct decreasing order of acidic strength of [1988]
(i) methanoic acid (ii) ethanoic acid
(iii) propanoic acid (iv) butanoic acid.

Solution:

An electron releasing substituent (+I effect) intensity the negative charge on the anion resulting in the decrease of stability and thus decreases the acidity of the acid. Hence acidic character decreases as the + I-effect of the alkyl group increases as

CH3 < CH3CH2 < CH3CH2CH2
< CH3CH2CH2CH2
Hence the order of acidic strength becomes:
(i) > (ii) > (iii) > (iv)

QUESTION: 4

Among the following the strongest acid is [1988]

Solution:

Chlorine is electron withdrawing group.
Further Inductive effect is stronger at α
position than β-position. i.e.,

QUESTION: 5

The compound formed when malonic ester isheated with urea is [1989]

Solution:

QUESTION: 6

The above shown polymer is obtained when acarbonyl compound is allowed to stand. It is awhite solid. The polymer is [1989]

Solution:

QUESTION: 7

The above compound describes a condensation polymer which can be obtained in two ways : either treating 3 molecules of acetone (CH3COCH3) with conc. H2SO4 or passing propyne (CH3 C ≡ CH) through a red hot tube.
The polymer is   [1989]

Solution:

Acetone forms mesitylene (1,3,5-trimethyl benzene) on distillation with conc. H2SO4.

QUESTION: 8

This polymer (B) is obtained when acetone issaturated with hydrogen chloride gas, B can be          [1989]

Solution:

When 3 molecules are combined in presence of dry HCl gas they condense to form phorone.

Note : Two molecules of acetone condense to form mesityl oxide.

QUESTION: 9

The reagent (s) which can be used to distinguishacetophenone from benzophenone is (are)       [1990]

Solution:

 I2 and NaOH react with acetophenone
(C6H5COCH3) to give yellow ppt. of CHIbut benzophenone (C6H5COC6H5) does not and hence can be used to distinguish between them. Oxidation of methyl ketones with sodium Hypoiodite (NaOI) or (I2 +NaOH) gives iodoform (CHI3) but not in case of benzophenone.

QUESTION: 10

Acetaldehyde reacts with [1991]

Solution:

Acetaldehyde reacts only with nucleophiles. Since the mobile p electrons of carbon– oxygen double bond are strongly pulled towards oxygen, carbonyl carbon is electrondeficient and carbonyl oxygen is electronrich.
The electron deficient (acidic) carbonyl
carbon is most susceptible to attack by
electron rich nucleophilic reagents, that is, by base. Hence the typical reaction of aldehydes and ketones is nucleophilic
addition.

QUESTION: 11

In which of the following, the number of carbonatoms does not remain same when carboxylic acidis obtained by oxidation [1992]

Solution:

Ketones on oxidation give carboxylic acids with lesser number of carbon atoms, i.e.,

QUESTION: 12

Benzoic acid gives benzene on being heated withX and phenol gives benzene on being heatedwith Y. Therefore X and Y are respectively [1992]

Solution:

QUESTION: 13

Sodium formate on heating yields [1993]

Solution:

QUESTION: 14

Among acetic acid, phenol and n-hexanol, whichof the following compounds will react withNaHCO3 solution to give sodium salt and carbondioxide ? [1993]

Solution:

Among acetic acid, phenol and n-hexanol only CH3 COOH reacts with NaHCO3 to evolve CO2 gas.

QUESTION: 15

(CH3)2 C = CHCOCH3 can be oxidized to (CH3)2C = CHCOOH by [1993]

Solution:

Chromic acid and KMnO4 will cleave the molecule at the site of double bond while Cu at 300°C cannot oxidise COCH3 COOH. The only reagent suitable for this conversion is NaOI or NaOH + I2 (iodoform
test):

QUESTION: 16

Pinacolone is [1994]

Solution:

Pinacolone is 3,3-dimethyl-2 butanone.

QUESTION: 17

Benzaldehyde reacts with ethanoic KCN to give[1994]

Solution:

When benzaldehyde is refluxed with aqueous alcoholic potassium cyanide, two molecules of benzaldehyde condense together to form benzain

QUESTION: 18

Aldehydes and ketones will not form crystallinederivatives with [1994]

Solution:

Dihydrogen sodium phosphate (NaH2PO4) does not have a lone pair of electrons on the P atom. As such it can not act as a nucleophile and hence does not react with aldehydes and ketones.

QUESTION: 19

Which of the following compound will undergoself aldol condensation in the presence of colddilute alkali ? [1994]

Solution:

Aldehydes which contain a α -hydrogen on a saturated carbon, i.e., CH3CH2CHO undergo aldol condensation.

QUESTION: 20

Formic acid is obtained when [1994]

Solution:

When glycerol is heated with oxalic acid
following reaction occurs.

QUESTION: 21

The preparation of ethyl acetoacetate involves[1994]

Solution:

Claisen condensation: Intermolecular
condensation of esters containing α-
hydrogen atom in presence of strong base to form β-keto ester

QUESTION: 22

Schotten-Baumann reaction is a reaction ofphenols with [1994]

Solution:

The function of NaOH is
(i) To convert phenol to more stronger
nucleophile PhO
(ii) To neutralize the acid formed

QUESTION: 23

An ester is boiled with KOH. The product iscooled and acidified with concentrated HCl. Awhite crystalline acid separates. The ester is[1994]

Solution:

Methyl acetate and ethyl acetate on
hydrolysis give CH3COOH which is a liquid. Similarly ethyl formate on hydrolysis will give formic acid which is also a liquid. Only ethyl benzoate on hydrolysis will give benzoic acid
which is a solid.

QUESTION: 24

Acetone reacts with iodine (I2) to form iodoformin the presence of [1995]

Solution:

Thus acetone reacts with iodine to form
iodoform in the presence of NaOH.

QUESTION: 25

In the Freidel Craft's acylation reaction, theeffective electrophile is [1996]

Solution: