Alcohols Phenols and Ethers Test

Result

Alcohols Phenols and Ethers Test - 49

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Weekly Quiz Competition

Question 1
1 / -0

The relative lowering of the vapour pressure of an aqueous solution containing a non-volatile solute is 0.0125. The molality of the solution is:

A
0.70

B
0.30

C
0.125

D
0.07

Solution

$$\bf{Explanation-}$$
From Roult's law, relative lowering of vapour pressure is given by
$$\dfrac{P^\circ - P_s}{P^\circ} = X_{solute}$$
Where, $$P^\circ $$= Vapour pressure of solvent
$$P_s$$ = Vapour pressure of solution
$$\dfrac{P^\circ - P_s}{P^\circ}$$ = Relative lowering of vapour pressure

Thus, $$X_{solute} = 0.0125$$

$$X_{solute} = \dfrac {mM}{1000 + mM}$$

Where, m= molarity and M = molar mass of aqueous solution.

$$0.0125 = \dfrac{m \times 18}{1000 + m \times 18}$$
$$12.5 + 0.225 m = 18 \times m$$
$$18 m - 0.225 m =12.5$$
$$ m = \dfrac{12.5} {17.775}$$
$$m = 0.70$$
So, morality of the solution is $$0.70 \ m$$

$$\bf{Conclusion-}$$ Hence, option A is correct.
Question 2
1 / -0

Which of the following alcohols will react with $${H}^{+}$$ with greatest ease?

A

B

C

D
Question 3
1 / -0

Alcohol can be dehydrated by:

A
$$(C{ H }_{ 3 }CO{ ) }_{ 2 }O$$

B
$$(C{ H }_{ 3 }{ ) }_{ 2 }S{ O }_{ 4 }$$

C
HI/P

D
Anhy$$ZnC{ l }_{ 2 }/\Delta $$

Solution

Option D is the correct answer.
$$R-CH_2-OH \xrightarrow{Anhy\ ZnCl_2/\Delta} R=CH_2$$
Question 4
1 / -0

In the reaction
$$ROH+PBr_{3} \rightarrow RBr$$
The number of moles of alcohol that may be converted into alkyl bromide by one mole of $$PBr_{3}$$ is:

A
$$1$$ mole

B
$$2$$ mole

C
$$3$$ mole

D
none of the above

Solution

From the balanced chemical equation, $$1$$ mole of $$ROH$$ reacts with $$1$$ mole of $$PBr_3$$ to form $$1$$ mole of $$RBr$$
Example:
$$3CH_3CH_2OH +PBr_3\xrightarrow{P+Br_2} 3CH_3CH_2Br + H_3PO_3$$
Question 5
1 / -0

Among the following compounds which can be dehydrated very easily?

A
$$CH_3CH_2CH_2CH_2CH_2OH$$

B
$$CH_3CH_2CH_2CH(OH)CH_3$$

C
$$CH_3CH_2CH(CH_3)CH_2CH_2OH$$

D
$$CH_3CH_2-(CH_3)C(OH)CH_2CH_3$$

Solution

The ease of dehydration of alcohols is tertiary > secondary > primary according to the order of stability of the carbocations.

The more stable carbocation is generated, thus more easily it will be dehydrated.

Option D is correct.
Question 6
1 / -0

How many carbon atom are present in third homologue of methyl ether?

A
$$1$$

B
$$2$$

C
$$3$$

D
$$4$$

Solution

Methyl ether is $$CH_{3}OCH_{3}$$
Next homologue is obtained by adding $$-CH_{2}$$ group i.e. $$CH_{3}OCH_{2}CH_{3}$$.
$$\therefore C$$ atoms$$=3$$
Again, adding 1 more $$-CH_{2}$$ group,
$$CH_{3}OCH_{2}CH_{2}CH_{3}$$
$$\therefore$$ Number of carbon atoms in 3rd homologue$$=4$$
Question 7
1 / -0

What is order of decreasing reactivities of following alcohols towards nucleophilic substitution with HBr ?

A

B

C

D

Solution

Higher the stability of carbocation, higher the reactivity towards Nucleophillic substitution with $$HBr$$.
If electron- donating group, is present higher the stability of carbocation.
Here, the above image is highly stable.
Question 8
1 / -0

Predict the major products (A) and (B).

A

B

C

D

Solution

On treatment of $$OMDM$$,the product will be trans and cis. But when treated by $${ H }_{ 3 }{ O }^{ \oplus }$$ ion it will not produce cis trans product.
Question 9
1 / -0

In the reaction, the product $$A$$ is:

A

B

C

D

Solution

This reaction is Pinnacol Pinnacolane type rearrangement reaction.
Option D is correct.
Question 10
1 / -0

Correct order of boiling point is:

A
Methanol < ethylene glycol < ethanol

B
Methanol < ethanol < ethylene glycol

C
Ethanol < ethylene glycol < methanol

D
Ethylene glycol < methanol < ethanol

Solution

Methanol $$<$$ Ethanol $$<$$ Ethylene glycol
Because large the molecular size, the higher the boiling point.
Option B is correct.