Hydrocarbons(12th Grade > Chemistry ) Questions and answers for exam Preparation

12th Grade > Chemistry

HYDROCARBONS MCQs

Total Questions : 28 | Page 2 of 3 pages

Question 11. The products obtained when 2 - methyl propene is oxidized with acidic potassium permanganate is

(CH3)2C=O,H−CHO
(CH3)2C=O,H2O,CO2
CH3COOH,H−CHO
CH3COOH,H2O,CO2

Discuss Question

Answer: Option B. -> (CH3)2C=O,H2O,CO2
:
B
Oxidation of 2-methylpropene, CH₃-C(CH₃)=CH₂, using hot, concentrated acidic potassium permanganate solution produces acetone (propan-2-one), carbon dioxide and water.

Question 12. Formation of 2-butene as major product by dehydration of 2-butanol is according to

Markownikoff rule
Saytzeff rule
Peroxide effect
Anti-Markownikoff rule

Discuss Question

Answer: Option B. -> Saytzeff rule
:
B

C H_{3} - C H - C H_{2} - C H_{3} \to C H_{3} - C H = C H - C H_{3} | 2 - B u t e n e O H 2 - B u t a n o l

According to this rule H atom goes from that

β

- carbon which is less hydrogenated.

Question 13. How many primary, secondary, tertiary and quaternary carbons are present in the following hydrocarbon

C H_{3} - C H (C H_{3}) - C (C H_{3})_{2} - C H_{2} - C H (C H_{3}) - C H_{2} - C H_{3}

6, 2, 2, 1
2, 6, 3, 0
2, 4, 3, 2
2, 2, 4, 3

Discuss Question

Answer: Option A. -> 6, 2, 2, 1
:
A

How Many Primary, Secondary, Tertiary And Quaternary Carbons...

Question 14.

C H_{3} C O O N a N a O H - --- \to C a O A O n e m o l e - ---- \to C l_{2} / h v B N a - -- \to E t h e r C (C H_{3} C O O)_{2} M n - --------- \to D

. Incorrect statement is

A and C are homologues
Salt of D on Kolbe's electrolysis gives C
C can exhibit conformational isomerism
B on reduction with Zn / HCl gives methane

Discuss Question

Answer: Option D. -> B on reduction with Zn / HCl gives methane
:
D
A is methane , B is

C H_{3} C l,

C is

C_{2} H_{6}

, D is

C H_{3} C O O H

Question 15. The octane number of a sample of petrol is 40. It means that its knocking property is equal to the mixture of

40% n-heptane + 60% iso-octane
40% petrol + 60% iso-octane
60% n-heptane + 40% iso-octane
60% petrol + 40% iso-octane

Discuss Question

Answer: Option C. -> 60% n-heptane + 40% iso-octane
:
C
Octane number of fuel is the percentage of iso- octane in mixture.

Question 16. Energy barrier between staggered and eclipsed conformation of ethane is?

0.6K Cal/ mole
2.9 K Cal/ mole
12 K Cal/ mole
16 K Cal/ mole

Discuss Question

Answer: Option B. -> 2.9 K Cal/ mole
:
B

Energy Barrier Between Staggered And Eclipsed Conformation O...

Question 17. n - hexane and n - heptane, when passed through

C r_{2} O_{3}

supported over alumina at

600^{0}

C respectively give

Benzene and heptane
Heptane and toluene
Phenol and benzene
Benzene and toluene

Discuss Question

Answer: Option D. -> Benzene and toluene
:
D
When n - hexane and n - heptane,are passed through

C r_{2} O_{3}

supported over alumina at

600^{0}

C respectively givebenzene and toluene.This reaction is called aromatisation.

Question 18. Assertion (A): -

N O_{2}

group is benzene ring deactivating and m - directing group
Reason (R): -

N O_{2}

group with draws electron density from benzene ring and makes ortho and para positions more electron deficient than meta position

A and R are true and R is the correct explanation of A
A and R are true and R is not the correct explanation of A
A is true, R is false
A is false but R is true

Discuss Question

Answer: Option A. -> A and R are true and R is the correct explanation of A
:
A
The Meta directing nature of Nitro group can be seen through its resonance structures:

Assertion (A): - NO2 group Is Benzene Ring Deactivating And...

Question 19. Major product formed during the reaction between isobutyl bromide and benzene in presence of anhydrous

A l C l_{3}

is :

isobutyl benzene
t- butyl benzene
n - butyl benzene
no reaction

Discuss Question

Answer: Option B. -> t- butyl benzene
:
B
1,2 - methyl shift takes place in isobutyl carbonium ion

Question 20. The order of decreasing reactivity towards an electrophilic reagent for the following
I. Benzene II. Toulene III. Chloro benzoic acid IV.Phenol