Hydrocarbons(11th And 12th > Chemistry ) Questions and answers for exam Preparation

11th And 12th > Chemistry

HYDROCARBONS MCQs

Total Questions : 30 | Page 1 of 3 pages

Question 1.

$C H_{3} C \equiv C H N a N H_{2} - ---- \to X C H_{2} C H_{2} B r - ------ \to Y .$ Identify the product 'Y' is

Pent - 2 - ene
Pent - 2 - yne
Pent - 1 - yne
Pentane

Discuss Question

Answer: Option B. -> Pent - 2 - yne
:
B

X is $C H_{3} - C \equiv C^{-} N a^{+}$

Y is $C H_{3} - C \equiv C - C H_{2} - C H_{3}$

The first step removes the terminal hydrogen from the given substrate (reactant on the left). Such a removable hydrogen is called an acidic hydrogen. In the next step, the nucleophile - which is rich in electrons - attacks the $C - B r$ bond of ethyl bromide. Because of the difference in electronegativity between carbon and bromine, this $C - B r$ bond is polar - meaning, the bonding electrons are closer to the more electronegative bromine. This gives rise to the possibility of the carbon of the $C - B r$ bond having a slight deficit of electrons; let's just say that this carbon misses electrons and that is where the electron-rich terminal carbon of $C H_{3} - C \equiv C^{-}$ comes in. Hence, the reaction.

Question 2.

The polymer used as electrodes in batteries is

polythene
polypropene
polyacetylene
poly vinyl chloride

Discuss Question

Answer: Option C. -> polyacetylene
:
C

A solid-state lithium/iodine battery has been formed by directly contacting metallic lithium with iodine-doped polyacetylene

Question 3.

Which of the following is correct order with respect to acidic nature :

$C H \equiv C H > C H_{3} - C \equiv C H > C H_{2} = C H_{2} > C H_{3} - C H_{3}$
$C H \equiv C H > C H_{2} = C H_{2} > C H_{3} - C \equiv C H > C H_{3} - C H_{3}$
$C H_{2} = C H_{2} > C H_{3} - C H_{3} > C H \equiv C H > C H_{3} - C \equiv C H$
$C H_{3} - C H_{3} > C H_{3} - C \equiv C H > C H_{2} = C H_{2} > C H \equiv C H$

Discuss Question

Answer: Option A. ->

C H \equiv C H > C H_{3} - C \equiv C H > C H_{2} = C H_{2} > C H_{3} - C H_{3}

:
A

sp hybridized carbon hydrogen is more acidic as it is more electronegative.

Question 4.

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 5.

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 6.

1,2 - Benzpyrene
1,2,5,6 -Dibenanthrecene
3 - Methyl anthracene
1,2 -Benzanthracene

Discuss Question

Answer: Option D. -> 1,2 -Benzanthracene
:
D
You should be able to see that the 3 benzene rings at the bottom form an anthracene.
And using the lowest locant rule, we can assign 1, 2 to the 2 carbons where benzene is attached.
So, the name would be 1,2-benzanthracene

Question 7.

The order of decreasing reactivity towards an electrophilic reagent for the following

I. Benzene II. Toulene III. Chloro benzoic acid IV.Phenol

IV > II > I > III
I > II > III > IV
II > IV > I > III
IV > II > II > I

Discuss Question

Answer: Option A. -> IV > II > I > III
:
A

OH group activates benezene ring more than - $C H_{3}$ group

Question 8.

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 9.

$P h C \equiv C - C H_{3} H_{3} O^{+} / H g^{+ 2} - ------- \to A$ . Then 'A' is

Discuss Question

Answer: Option A. ->

:
A

addition of water followed by tautomerism

Question 10.

$(C H_{3})_{3} C H K M n O_{4} - ---- \to A; C H_{3} (C H_{2})_{2} C H_{3} H C l - -- \to A l C l_{3} B; C H_{3} (C H_{2})_{4} C H_{3} C r_{2} O_{3}, 773 K - ------ \to 10 - 20 a t m C;$