This set of Engineering Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Electromeric Effect”.
1. Which of the following is a temporary effect brought into play at the requirement of attacking reagent?
a) Inductive effect
b) Mesomeric effect
c) Electromeric effect
d) Inductomeric effect
View Answer
Explanation: Electromeric effect is a temporary effect brought into play at the requirement of attacking reagent. Electromeric effect refers to a molecular polarizability effect occurring by an intra-molecular electron displacement.
2. Select the correct statement from the following option.
a) When multiple bonds are present between two different atoms, electromeric shift towards the more electronegative atom takes place
b) When multiple bonds are present between two similar atoms, the first possibility is symmetric alkenes or alkynes
c) When multiple bonds are present between two similar atoms, the second possibility is asymmetric alkenes or alkynes
d) All of the mentioned
View Answer
Explanation: When multiple bonds are present between two different atoms, electromeric shift towards the more electronegative atom takes place. When multiple bonds are present between two similar atoms, the first possibility is symmetric alkenes or alkyne and the second possibility is asymmetric alkenes or alkynes.
3. Select the correct statement from the following option.
a) Conjugate effect is stronger than (-I) effect
b) Conjugate effect is weaker than (-I) effect
c) Conjugate effect is same as (-I) effect
d) None of the mentioned
View Answer
Explanation: Conjugate effect is stronger than (-I) effect. Conjugate effect (or delocalization) is an effect in which molecular orbitals (MOs) are conjugated to new molecular orbitals that are more delocalized and therefore generally lower in energy.
4. When the complete transfer of π-electrons take place away from the atom at the requirement of attacking agent, it is called __________
a) (-E) effect
b) (+E) effect
c) (-I) effect
d) (+I) effect
View Answer
Explanation: When the complete transfer of π-electrons takes place away from the atom at the requirement of attacking agent, it is called (+E) effect.
5. The positively charged and electron deficient compounds which have a tendency to form a bond by accepting the electron pair are known as __________
a) Electrophiles
b) Nucleophiles
c) Homophiles
d) All of the mentioned
View Answer
Explanation: The positively charged and electron deficient compounds which have a tendency to form a bond by accepting the electron pair are known as electrophiles.
6. Which of the following is an example of lewis base?
a) ZnCl2
b) BF3
c) NH3
d) FeCl2
View Answer
Explanation: NH3 is an example of lewis base and ZnCl2, BF3 and FeCl2 are the examples of lewis acid.
7. Which of the following is an incorrect statement about the nucleophiles?
a) They are electron rich
b) They possess an empty orbital to receive the electron pair
c) They attack electron deficient centres
d) Examples are: OH–, NH3, H2O etc
View Answer
Explanation: Nucleophiles possess an unshared electron pair which is not firmly held to the nucleus. All the other options are correct. They are electron rich and attack on electron deficient centres. Examples are: OH–, NH3, H2O etc.
8. Lewis acids are examples of nucleophilic reagents.
a) True
b) False
View Answer
Explanation: Lewis acids are the examples of electrophilic reagents and Lewis bases are the examples of nucleophilic reagents.
9. Those groups which are electron repelling and have lesser electron attracting power than hydrogen show __________
a) (+E) effect
b) (-E) effect
c) (-I) effect
d) (+I) effect
View Answer
Explanation: Those groups which are electron repelling and have lesser electron attracting power than hydrogen show (+I) effect.
10. Which of the following molecule will show highest dipole moment?
a) CH3Cl
b) CH3Br
c) CH3F
d) CH3I
View Answer
Explanation: CH3F will show the highest dipole moment because it is the most electronegative compound.
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