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 Multiple Choice QuestionsMultiple Choice Questions

231.

Iodoform test is not given by :

  • HCHO

  • CH3CHO

  • CH3COCH3

  • C2H5OH


A.

HCHO

Iodoform test is given by those compounds which have -CO-CH3 gorup or on oxidation yields this group.

Formaldehyde does not have -CO-CH3 group. It does not give iodoform test.


232.

When AgCl is treated with KCN

  • Ag is precipitated

  • a complex ion is formed

  • double decomposition takes place

  • no reaction takes place


B.

a complex ion is formed

When AgCl is treated with with KCN, a complex ion is formed.

AgCl + 2KCN → K[Ag(CN)2] + KCl


233.

Which reaction is used for the preparation of acetophenone ?

  • Reimer-Tiemann reaction

  • Wurtz-Fittig reaction

  • Friedel-Craft's reaction

  • Cannizaro's reaction


C.

Friedel-Craft's reaction

Acetophenone can be prepared by Friedel-Craft's reaction. By treating benzene with acetyl chloride in presence of anhydrous aluminium chloride acetophenone is obtained.

C6H5Benzene + ClCOCH3Acetyl alcohol Anhydrous AlCl3 C6H5COCH3Acetophenone + HCl


234.

The correct statement regarding the following compounds is

  • all three compounds are chiral

  • only I and II are chiral

  • I and III are diastereomers

  • only I and III are chiral


D.

only I and III are chiral

Here, the image has 2-R, 3-R configuration. Hence, it is a chiral compound.

Here, the image has 2-R, 3-S configuration, i.e. it has plane of symmetry or in other words, rotation of half part is cancelled by the other half. Hence, it is not a chiral compound.

Here, the image has 2-S, 3-S configuration. Hence, it is also a chiral compound.


235.

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

  • CH3CHO

  • PhCOCH3

  • PhCOPh

  • CH3COCH3


A.

CH3CHO

Carbonyl compounds undergoes nucleophilic addition reaction.

[X- shows negative inductive effect]

If group or atom attached with carbonyl carbon shows negative inductive effect, then it decreases electron density on carbonyl carbon and facilitate the attack of nucleophiles, hence reactivity of carbonyl compound increases.

[Y- shows negative inductive effect]

If group or atom attached with carbonyl carbon shows positive inductive effect, then it increases electron density on carbonyl carbon and supress the attack of nucleophiles, hence, reactivity of carbonyl compound decreases.

The aromatic aldehydes and ketones are less reactive than their aliphatic analogues. This is due to the +R effect of benzene ring.

On the basis of above informations, the increasing order of the nucleophilic addition reaction in the following compound will be CH3CHO > CH3COCH3 > PhCOCH3 > PhCOPh


236.

Pure methane can be produced by

  • Wurtz reaction

  • Kolbe's electrolytic method

  • soda lime decarboxylation

  • reduction with H2


C.

soda lime decarboxylation

Methane cannot be produced by Wurtz reaction, Kolbe's electrolytic method and reduction with Hbecause, it has one carbon atom. Pure methane can be produced by the decarboxylation of sodium acetate.

CH3COONa + NaOHCaOHCH4 +Na2CO3


237.

Boiling water reacts with C6H5N2+Cl- to give

  • aniline

  • benzylamine

  • phenol

  • benzaldehyde


C.

phenol

Boiling water reacts with C6H5N2+Cl- to give phenol.

C6H5N2+Cl- BoilH2O C6H5OH (SNAr mechanism)


238.

The ease of dehydrohalogenation of alkyl halide with alcoholic KOH is:

  • 3° < 2° < 1°

  • 3° > 2° > 1 °

  • 3° < 2° > 1°

  • 3° > 2° < 1 °


B.

3° > 2° > 1 °

According to Saytzeff rule, any alkyl halide that gives a more highly substituted (more stable) alkene undergoes dehydrohalogenation faster than the one which gives a less highly substituted (less stable) alkene. Thus, the ease of dehydrohalogenation of different alkyl halides having the· same halogen decreases in the order,

tertiary (3°) > secondary (2°) > primary (1°).