Practice Start Test

Basics of Organic Chemistry (GOC)

JEE Chemistry · 87 questions · Page 2 of 9 · Click an option or "Show Solution" to reveal answer

Q11
Given below are two statements : Statement I : A mixture of chloroform and aniline can be separated by simple distillation. Statement II : When separating aniline from a mixture of aniline and water by steam distillation aniline boils below its boiling point. In the light of the above statements, choose the most appropriate answer from the options given below :
A Both Statement I and Statement II are true
B Both Statement I and Statement II are false
C Statement I is true but Statement II is false
D Statement I is false but Statement II is true
Correct Answer
Option A
Solution

Mixture of chloroform and aniline can be separated by simple distillation as these two liquids have sufficient difference in boiling point.

Chloroform (b.p.

334 K), aniline (b.p.

457 K) In steam distillation, if one of the substances is water and the other, a water insoluble substance (like aniline) then the mixture will boil close to but below 373 K.

Q12
In chromotography technique, the purification of compound is independent of :
A Solubility of the compound
B Mobility or flow of solvent system
C Physical state of the pure compound
D Length of the column or TLC plate
Correct Answer
Option C
Solution

The purification of a compound using chromatography is dependent on several factors, including the solubility of the compound, the mobility or flow of the solvent system, and the length of the column or TLC plate.

However, it is not typically dependent on the physical state of the pure compound.

Here's why : Option A : The solubility of the compound in the mobile phase and its interaction with the stationary phase are key factors in determining how the compound will migrate in a chromatographic system.

Hence, the solubility of the compound does affect its purification.

Option B : The mobility or flow of the solvent system, often referred to as the mobile phase in chromatography, also plays a significant role in the separation of components in the mixture.

The rate at which the mobile phase moves can influence how far and how quickly the components of the mixture will travel.

Option C : The physical state (solid, liquid, gas) of the pure compound is usually not a factor in the purification process in chromatography.

Whether a compound is solid, liquid, or gas does not typically affect its ability to be separated by chromatography, as it is the interactions between the compound and the stationary/mobile phases that are key.

Option D : The length of the column or TLC plate can impact the degree of separation achieved in chromatography.

A longer column or TLC plate can provide more opportunities for the interactions that drive the separation process, often leading to better separation of the components.

So, Option C is correct : The physical state of the pure compound is usually not a factor in its purification by chromatography.

Q13
Given below are two statements : Statement I : Hyperconjugation is a permanent effect. Statement II : Hyperconjugation in ethyl cation (CH3−C+H2)\left( {C{H_3} - \mathop C\limits^ + {H_2}} \right) involves the overlapping of Csp2−H1s{C_{s{p^2}}} - {H_{1s}} bond with empty 2p orbital of other carbon. Choose the correct option :
A Both statement I and statement II are false
B Statement I is incorrect but statement II is true
C Statement I is correct but statement II is false
D Both statement I and statement II are true.
Correct Answer
Option C
Solution

Statement I : It is correct statement Statement II :

CH3−CH2⊕C{H_3} - \mathop {C{H_2}}\limits^ \oplus

involve

Csp3−H1s{C_{s{p^3}}} - {H_{1s}}

bond with empty 2p orbital hence given statement is false.

Q14
Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R) : Assertion (A) : A simple distillation can be used to separate a mixture of propanol and propanone. Reason (R) : Two liquids with a difference of more than 20∘^\circ in their boiling points can be separated by simple distillations. In the light of the above statements, choose the most appropriate answer from the options given below :
A (A) is false but (R) is true.
B Both (A) and (R) are correct but (R) is not the correct explanation of (A)
C (A) is true but (R) is false
D Both (A) and (R) are correct and (R) is the correct explanation of (A).
Correct Answer
Option D
Solution

Simple distillation can be used to separate a mixture of propanol and propanone.

• Two liquid with difference in B.P. around 20°C can be separated by simple distillation.

• B.P. of propanol is 370 K.

B.P. of acetone is 329 K.

Both assertion & reason are correct & (R) is the correct explanation of (A).

Q15
Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : A mixture contains benzoic acid and napthalene. The pure benzoic acid can be separated out by the use of benzene. Reason R : Benzoic acid is soluble in hot water. In the light of the above statements, choose the most appropriate answer from the options given below.
A Both A and R are true and R is the correct explanation of A.
B Both A and R are true but R is NOT the correct explanation of A.
C A is true but R is false.
D A is false but R is true.
Correct Answer
Option D
Solution

Since, both benzoic acid and naphthalene will dissolve in benzene.

Hence assertion is wrong.

Benzoic acid is almost insoluble in cold water but soluble in hot water.

Hence Reason is true.

Q16
Using column chromatography, mixture of two compounds 'A' and 'B' was separated. 'A' eluted first, this indicates 'B' has
A high Rf, weaker adsorption
B high Rf, stronger adsorption
C low Rf, weaker adsorption
D low Rf, stronger adsorption
Correct Answer
Option D
Solution

In column chromatography, the compound that elutes first is the one that is less strongly adsorbed to the stationary phase.

Hence, 'A' has weaker adsorption than 'B'.

Therefore, 'B' has stronger adsorption.

The retention factor (Rf) is a measure of how much a compound moves up the column; a higher Rf means the compound travels further and is less strongly adsorbed to the stationary phase.

Since 'A' elutes first, 'A' has a higher Rf than 'B'.

Hence, 'B' has a lower Rf.

So, the correct answer is 'Option D: low Rf, stronger adsorption'.

Q17
Arrange the following in increasing order of reactivity towards nitration A. p-xylene B. bromobenzene C. mesitylene D. nitrobenzene E. benzene Choose the correct answer from the options given below
A C < D < E < A < B
B D < B < E < A < C
C D < C < E < A < B
D C < D < E < B < A
Correct Answer
Option B
Solution

The correct order of reactivity towards nitration is as electron releasing groups on benzene ring facilitate the nitration at benzene ring.

Q18
Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R Assertion A : Thin layer chromatography is an adsorption chromatography. Reason R : A thin layer of silica gel is spread over a glass plate of suitable size in thin layer chromatography which acts as an adsorbent. In the light of the above statements, choose the correct answer from the options given below
A Both A and R are true and R is the correct explanation of A
B Both A and R are true but R is NOT the correct explanation of A
C A is true but R is false
D A is false but R is true
Correct Answer
Option A
Solution

Thin layer chromoatography (TLC) is another type of adsorption chromatography, which involve sepration of substance of a mixture ovel a thin layer of an adsorbent coated on glass plate.

A thin layer (about 0.2 mm thick) of an adsorbent (silica gel) or (Alumina) in spread overa glass plate of suitable size.

Hence Assertion (A) is correct and Reason (R) is correct explanation of (A)

Q19
The descending order of acidity for the following carboxylic acid is- A. CH3COOH\mathrm{CH}_{3} \mathrm{COOH} B. F3C−COOH\mathrm{F}_{3} \mathrm{C}-\mathrm{COOH} C. ClCH2−COOH\mathrm{ClCH}_{2}-\mathrm{COOH} D. FCH2−COOH\mathrm{FCH}_{2}-\mathrm{COOH} E. BrCH2−COOH\mathrm{BrCH}_{2}-\mathrm{COOH} Choose the correct answer from the options given below:
A B > C > D > E > A
B D > B > A > E > C
C B > D > C > E > A
D E > D > B > A > C
Correct Answer
Option C
Solution

The acidity of carboxylic acids is influenced by the electron-withdrawing ability of the groups attached to the carboxylic acid.

The stronger the electron-withdrawing ability of the group, the more it stabilizes the carboxylate anion (formed after losing the acidic proton), and hence the stronger the acid.

Let's look at the groups attached to the carboxylic acid in each option: A.

CH3−\mathrm{CH}_{3}\mathrm{-}

: Methyl group. It's electron-donating due to the hyperconjugation effect. B.

F3C−\mathrm{F}_{3}\mathrm{C}-

: Trifluoromethyl group.

Strong electron-withdrawing group due to the electronegativity of fluorine atoms and inductive effect.

C.

ClCH2−\mathrm{ClCH}_{2}-

: Chloromethyl group.

It has some electron-withdrawing ability due to the electronegativity of the chlorine atom, but it's less than that of fluorine.

D.

FCH2−\mathrm{FCH}_{2}-

: Fluoromethyl group.

It has electron-withdrawing ability due to the electronegativity of the fluorine atom, but less than that of the trifluoromethyl group.

E.

BrCH2−\mathrm{BrCH}_{2}-

: Bromomethyl group.

It has some electron-withdrawing ability due to the electronegativity of the bromine atom, but it's less than that of chlorine and fluorine.

So the order of acidity will be: B > D > C > E > A

Q20
The incorrect statement regarding conformations of ethane is :
A The dihedral angle in staggered conformation is 60∘60^{\circ}.
B Ethane has infinite number of conformations.
C Eclipsed conformation is the most stable conformation.
D The conformations of ethane are inter-convertible to one-another.
Correct Answer
Option C
Solution

The statement regarding conformations of ethane that is incorrect is: Option C - Eclipsed conformation is the most stable conformation.

To explain why Option C is incorrect, let's analyze all the options: Option A: "The dihedral angle in staggered conformation is

60∘60^{\circ}

."

This statement is incorrect.

In staggered conformation, the dihedral angle, or the angle between the planes containing the hydrogen atoms, is actually

60∘60^{\circ}

.

However, the staggered form is not unique; it refers to the form where any given pair of hydrogens on adjacent carbons has this dihedral angle, but rotating the molecule can yield a variety of staggered conformations with different specific hydrogen atoms at the

60∘60^{\circ}

dihedral angle. The full rotation of one ethyl group relative to the other through

360∘360^{\circ}

creates a cycle where the staggered conformation occurs every

120∘120^{\circ}

.

Option B: "Ethane has infinite number of conformations."

This statement is correct.

The rotation around the carbon-carbon single bond (sigma bond) is relatively free, so ethane can theoretically adopt an infinite number of conformations between the two extremes of staggered and eclipsed.

These conformations can have very slight differences in angles, resulting in finely varied overlap of electron clouds.

Option C: "Eclipsed conformation is the most stable conformation."

This statement is incorrect, which makes it the answer to the question.

The eclipsed conformation is actually the least stable conformation of ethane due to the increased torsional strain from electron repulsion.

The electron clouds of the bonding pairs of hydrogens on adjacent carbons are aligned in such a way as to be as close to each other as possible, increasing repulsion.

The most stable conformation is the staggered conformation, where the groups are as far apart as possible, reducing repulsion.

Option D: "The conformations of ethane are inter-convertible to one-another."

This statement is correct.

As you rotate around the carbon-carbon single bond, the conformations continuously change from one to another.

This interconversion can be quite rapid and occurs without the need for a high energy input under normal conditions.

Thus, the incorrect statement is Option C.

Ready for a full JEE mock test? Timed · full syllabus · instant results
Take a Mock Test →