chemistry : class11 Dipole Moment : Polar character of covalent bond : Chemical Bonding and Molecular Structure MCQ Questions and Answers
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Dipole Moment
MCQ questions and answers.
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MCQ Questions
1. What is the dipole moment of a nonpolar covalent bond?
A.
Zero
B.
Equal to one
C.
Always negative
D.
Always infinite
Correct Answer:
Zero
Explanation:
In a nonpolar covalent bond, electrons are shared equally, so the centers of positive and negative charges coincide and the dipole moment is zero.
2. The SI unit of dipole moment is:
A.
Coulomb metre
B.
Coulomb per metre
C.
Newton metre
D.
Joule per coulomb
Correct Answer:
Coulomb metre
Explanation:
Dipole moment is given by charge multiplied by distance, so its SI unit is coulomb metre (C m).
3. The dipole moment of a bond is commonly represented by the expression:
A.
μ = q × r
B.
μ = q ÷ r
C.
μ = r ÷ q
D.
μ = q + r
Correct Answer:
μ = q × r
Explanation:
The magnitude of dipole moment is the product of the magnitude of charge and the distance between the centers of positive and negative charges.
4. Which molecule has zero net dipole moment because of its symmetrical structure?
A.
CO2
B.
H2O
C.
NH3
D.
HCl
Correct Answer:
CO2
Explanation:
CO2 has polar C=O bonds, but its linear symmetrical structure causes the bond dipoles to cancel, giving zero net dipole moment.
5. Which of the following molecules has a permanent dipole moment?
A.
HCl
B.
Cl2
C.
N2
D.
O2
Correct Answer:
HCl
Explanation:
HCl contains atoms with different electronegativities, producing an unequal charge distribution and a permanent dipole moment.
6. The dipole moment of a homonuclear diatomic molecule such as H2 is:
A.
Zero
B.
One debye
C.
Greater than that of HCl
D.
Always positive
Correct Answer:
Zero
Explanation:
The two identical atoms in H2 have equal electronegativity, so the bond is nonpolar and its dipole moment is zero.
7. If the magnitude of charge in a dipole increases while the distance remains constant, the dipole moment:
A.
Increases
B.
Decreases
C.
Becomes zero
D.
Remains unchanged
Correct Answer:
Increases
Explanation:
Since dipole moment is μ = q × r, increasing the charge q increases the dipole moment when the distance r is constant.
8. The commonly used unit for expressing molecular dipole moments is:
A.
Debye
B.
Pascal
C.
Kelvin
D.
Angstrom per mole
Correct Answer:
Debye
Explanation:
Although the SI unit is coulomb metre, molecular dipole moments are commonly expressed in debye (D).
9. What is the net dipole moment of a molecule when all its bond dipoles cancel each other?
A.
Zero
B.
Maximum
C.
Equal to the largest bond dipole
D.
Always negative
Correct Answer:
Zero
Explanation:
Dipole moment is a vector quantity. When equal and opposite bond dipoles cancel, the molecule has zero net dipole moment.
10. Which factor directly affects the magnitude of a dipole moment?
A.
Charge separation
B.
Molecular mass only
C.
Boiling point only
D.
Number of neutrons only
Correct Answer:
Charge separation
Explanation:
Dipole moment depends on the magnitude of separated charges and the distance between them, together called charge separation.
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