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Topic Question Set

Q 1 :    

Which of the following compounds will give silver mirror with ammonical silver nitrate?

(A) Formic acid
(B) Formaldehyde
(C) Benzaldehyde
(D) Acetone

Choose the correct answer from the options given below:                           [2024]

  • A only

     

  • B and C only

     

  • C and D only

     

  • A, B, and C only

     

(4)

Aldehydes give positive Tollen's test.

RCHO+2[Ag(NH3)2]++3OH-→RCOO-+2Ag+2H2O+4NH3

So formaldehyde (HCHO) and benzaldehyde (C6H5CHO) give silver mirror with ammonical silver nitrate solution.

Formic acid has aldehydic part in it. So it also gives positive Tollen's as well as Fehling's test.

HCOOH+2[Ag(NH3)2]++2OH-→CO2+2Ag+2H2O+4NH3

Co2+→H2S gasCoS↓ (Black ppt.)

                           (A)

 

Q 2 :    

From the compounds given below, number of compounds which give positive Fehling’s test is ______.

Benzaldehyde, Acetaldehyde, Acetone, Acetophenone, Methanal, 4-nitrobenzaldehyde, cyclohexane carbaldehyde.              [2024]


(3)

 

Q 3 :    

The compounds which give positive Fehling’s test are:               [2025]

Choose the correct answer from the options given below:

  • (A), (D) and (E) only

     

  • (C), (D) and (E) only

     

  • (A), (B) and (C) only

     

  • (A), (C) and (D) only

     

(2)

Fehling’s test is given by those aldehydes which have α–hydrogen atom. Benzaldehyde (A) has no α–hydrogen atom, hence does not give Fehling’s test. Acetophenone (B) is a ketone and ketones do not give Fehling’s test. (D) and (E) are aldehydes with α–hydrogen atom and C tautomerises to an aldehyde.

Thus C, D and E give positive Fehling’s test.

 

Q 4 :    

Both acetaldehyde and acetone (individually) undergo which of the following reactions?       [2025]

(A) Iodoform Reaction
(B) Cannizzaro Reaction
(C) Aldol Condensation
(D) Tollen’s Test
(E) Clemmensen Reduction

Choose the correct answer from the options given below:

  • (A), (B) and (D) only

     

  • (A), (C) and (E) only

     

  • (B), (C) and (D) only

     

  • (C) and (E) only

     

(2)

Reaction Acetaldehyde Acetone
A. Iodoform (given by Ar/R–CO–CH3) + +
B. Cannizzaro (given by aldehydes without αH) – –
C. Aldol (given by aldehydes with αH) + +
D. Tollen’s test (given by aldehydes) + –
E. Clemmensen reduction (given by carbonyl compounds) + +

 

Q 5 :    

Given below are two statements:              [2025]

In the light of the above statements, choose the most appropriate answer from the options given below:

  • Statement I is incorrect but Statement II is correct

     

  • Statement I is correct but Statement II is incorrect

     

  • Both Statement I and Statement II are incorrect

     

  • Both Statement I and Statement II are correct

     

(2)

Phenols are soluble in NaOH (as phenols are more acidic than H2O). Aldehydes show Tollen’s test. As Vanillin contains both phenolic group and aldehydic group, it reacts with NaOH as well as Tollen’s reagent. Vanillin does not show aldol condensation as there are no hydrogens on carbon alpha to carbonyl group.

 

Q 6 :    

“P” is an optically active compound with molecular formula C6H12O. When “P” is treated with 2,4-dinitrophenylhydrazine, it gives a positive test. However, in presence of Tollens reagent, “P” gives a negative test. Predict the structure of “P”.            [2025]

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  •  

  •  

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(2)

Compound Optical activity Tollen’s test (given by aldehydes) 2,4 DNP test (given by aldehydes and ketones)
Inactive
Negative Positive
Active Negative Positive
Active Positive Positive
Inactive Negative Positive