In chemistry, polarity can be defined as something that holds atoms together. Furthermore, in a chemical bonding, atoms share electrons with one another in order to bond. A polar molecule is formed when one of the atoms exerts a strong, attractive force on the electrons in the bond.
| Definition: Polarity is a separation of electric charge that results in a molecule or its chemical groups having an electric dipole moment with a negatively charged and positively charged end. |
Polarity Chemistry Questions with Solutions
Q-1: Polarity in a molecule arises due to _________.
a) No difference in electronegativity between the bonded atoms
b) Non-zero electric dipole moment
c) No electric dipole moment
d) Same atoms being bonded together
Answer: b) Non-zero electric dipole moment
Explanation: A molecule must have a non-zero or permanent electric dipole moment in order to be polar.
Q-2: Which of the following liquids dissolve in each other?
a) Toluene + Water
b) Toluene + Benzene
c) Both a) and b)
d) Water + Benzene
Answer: b) Toluene + Benzene
Explanation: Because both toluene and benzene are nonpolar, they dissolve in each other in accordance to dissolve like the principle.
Q-3: C2H5OH is the chemical formula for ethanol. Which of these two atom’s bonds in this compound is the least polar?
a) C-H
b) O-H
c) C-O
d) C-C
Answer: d) C-C
Explanation: Polarity in a bond is caused by electronegativity differences between the bonded atoms. The greater the difference in electronegativity, the greater the polarity. Because both bonded atoms in a C-C bond are the same, there is no difference in electronegativity between them. Hence, the C-C bond is the least polar bond.
Q-4: Dipole moment is the measure of _________ in a molecule.
a) Electronegativity difference
b) Polarity
c) Charge separation
d) Bond strength
Answer: b) Polarity
Explanation: The dipole moment is a measure of the polarity of chemical bonds that exist between two atoms in a molecule. The separation of negative and positive charges occurs during the dipole moment.
Q-5: What can you say about the polarity of BrF5?
Answer: The molecular geometry of bromine pentafluoride is square pyramidal. The presence of a lone pair creates an unbalanced region of negative charge. As a result of its structural asymmetry, it is a polar molecule.
Q-6: What are the polarity and molecular shape of xenon tetrafluoride?
a) Square pyramidal, nonpolar
b) Square planar, nonpolar
c) Tetrahedral, nonpolar
d) Tetrahedral, polar
Answer: b) Square planar, nonpolar
Explanation: The structure of xenon tetrafluoride is given below:
To predict the molecular shape, we must first determine the steric number of the xenon atom.
Steric number = Number of lone pairs on Xe-atom + Number of sigma bonds made by Xe
Steric number = 2+4 = 6
A steric number of 6 corresponds to the hybridisation sp3d2, which corresponds to the square planar shape according to VSEPR.
The structure clearly shows that the dipole moment of all the Xe-F bonds will be nullified, and the lone pairs will also cancel out each other, resulting in a nonpolar molecule.
Q-7: What best describes the molecule H2S in terms of polarity?
a) A nonpolar molecule with polar covalent bonds.
b) A polar molecule composed of nonpolar covalent bonds.
c) A polar molecule composed of polar covalent bonds.
d) A nonpolar molecule with nonpolar covalent bonds.
Answer: c) A polar molecule composed of polar covalent bonds.
Explanation: H2S is a polar molecule due to its bent geometrical structure, and the small difference in electronegativity between hydrogen(2.1) and sulphur(2.5) results in a non-zero dipole moment. Polar covalent bonds are formed when atoms with slightly different electronegativity values come together.
Q-8: Why are some solutes soluble in water while others are soluble in cyclohexane?
Answer: Only polar solutes are soluble in polar water because their polarities are identical. Similarly, nonpolar solutes are soluble in nonpolar cyclohexane because their polarities are the same.
Q-9: Arrange the following bonds in the order of increasing polarity.
C-H, F-H, N-H, O-H
Answer: C-H<N-H<O-H<F-H
Explanation: The greater the difference in electronegativity between the bonded atoms, the greater the polarity. Check the electronegative order of C, F, N, and O because H is common in all. The greater the electronegativity, the greater the electronegativity difference. Fluorine has the highest electronegative potential, while carbon has the lowest. As a result, the correct sequence is C-H<N-H<O-H<F-H.
Q-10: Which of the following atoms, when bonded to a fluorine atom, produces the highest degree of polarity?
a) Sulphur
b) Hydrogen
c) Carbon
d) Oxygen
Answer: b) Hydrogen
Explanation: We know that the greater the electronegativity difference in the bonded atoms, the greater the degree of polarity. When fluorine is bonded to hydrogen, the electronegativity difference is 1.9. Hence, the H-F bond produces the highest degree of polarity.
Q-11: What are some of the properties of water determined by its polarity?
Answer: Water has high cohesion properties due to its polarity, which means it sticks strongly to similar molecules. It is referred to as the universal solvent because it can dissolve anything found in nature due to its polar nature. Water capillary action through bloodstreams and plant roots is also enabled by polarity.
Q-12: Is CH4 a polar or nonpolar molecule?
Answer: Because CH4 has symmetrical tetrahedral geometry, it has a zero dipole moment and is thus nonpolar.
Q-13: Which of the following statements is correct?
1. If the diatomic molecule’s bond is polar, it is polar.
2. The polarity of the molecule has a significant impact on physical properties such as boiling point.
Answer: Both the statements are true.
Explanation: If the bond between the bonded atoms is polar, the molecule is said to be polar. The boiling point of a molecule is directly proportional to its polarity. The greater the polarity, the greater the boiling point.
Q-14: Which of the following is the polar molecule?
a) Carbon dioxide
b) Beryllium chloride
c) Sulphur dioxide
d) All of the above
Answer:c) Sulphur dioxide
Explanation: Sulphur dioxide is polar. Because of the “bent” molecular geometry, the molecule has a non-zero dipole moment. Since it has a dipole moment, it is polar in nature.
Q-15: What is the polarity of the acetone molecule? What functional group is present in it?
Answer: Acetone(CH3COCH3) is a polar substance due to polarity in the carbonyl group caused by the difference in electronegativity of oxygen and carbon atoms. Ketone(-CO) functional group is present in it.
Practice Questions on Polarity
Q-1: Which of the following ionic bonds has the highest degree of polarity?
a) Li-O
b) Li-F
c) K-Cl
d) K-Br
Q-2: How could the BeCl2 bonds be classified based on bond polarity?
a) Polar covalent
b) Nonpolar covalent
c) Ionic
d) Covalent
Q-3: In the following diatomic molecules, identify the end of the molecule that is positive relative to the other end.
a) BrF
b) ICl
c) HF
Q-4: What is the significance of the dipole moment in water molecules?
Q-5: Predict the C2H2 molecule’s shape and polarity.
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