Chemistry MCQs for NEET — Practice Questions with Answers

(d) An electrophile is defined as electron deficient species which attacks on electron rich areas. Being electron deficient, the electrophiles behaves an Lewis acids.

e.g. H+, CI+, Br+, NO2+ NO+ etc.

The electrophiles can be seen in the form of neutral molecules also e.g. :CR₂, N..R,BF₃ etc.

Thus, we can say that electrophile can be either neutral or positively charged species and can form a bond by accepting a pair of electrons from a nucleophile.

(d) Isomers which are possible by rotation about single bonds without cleavage of any bond are called conformers. In ethane, an infinite number of conformations are possible. There are two extreme forms, the staggered conformation, which is the most stable and the eclipsed conformation which is least stable. Among the conformers of ethane, bond angle and bond length remain same while their energy, stability and dihedral angle are different.

(b) Greater the s-character of C-atom in hydrocarbons, greater the electronegativity of

that carbon and thus greater the acidic nature of the H attached to electronegative carbon.

                        CH≡CH CH₂=CH₂ CH₃-CH₃

Hybridisation:         sp        sp2        sp3

s-character:          50%      33%       25%

Electronegativity:     â†Max.---------------------------------------

Acidic character      â†Max.---------------------------------------

of terminal H

Thus, CH≡CH > CH₃C≡CH > CH₂=CH₂ > CH₃-CH₃

(d) Steam distillation is used to purify the substances which

(i) are volatile in steam but are immiscible with water.

(ii) possess sufficiently high vapour pressure at the boiling point of water.

(iii) contain non- volatile impurities.

The process of steam distillation can also be used to separate a mixture of two organic compounds one of which is steam volatile while the other is not. In ortho and para-nitrophenols, the latter is non-volatile, hence they are separated by steam distillation.

The staggered conformation of ethane is more stable than the eclipsed conformation because it has no torsional strain. In the staggered conformation, the hydrogen atoms are arranged in a way that minimizes the steric repulsion between them, resulting in lower potential energy.

Toluene is the most reactive towards electrophilic nitration among the given options. The methyl group being an electron-donating substituent activates the benzene ring, making it more susceptible to electrophilic attack by the nitro group.

The correct order of decreasing acid strength is: trifluoroacetic acid (B) > trichloroacetic acid (A) > formic acid (D) > acetic acid (C). The highly electronegative fluorine and chlorine atoms withdraw electrons, making the respective acids stronger than acetic and formic acids.

$$\begin{gathered} \frac{P_1{V}_1}{T_1}=\frac{P_2{V}_2}{T_2} \left(Here, P_1=715-15=700 mm\right) \\ \frac{700\times 55}{300}=\frac{760\times V_2}{273} \\ {V}_2=46 ml at NTP \\ \% of N=\frac{28}{22400}\times \frac{volume of{N}_2 at NTP\left(in ml\right)}{weight of organic compound \left(in g\right)}\times 100 \\ =\frac{28}{22400}\times \frac{46}{0.35}\times 100=16.45 \end{gathered}$$