Question

Identify the number of molecules having permanent dipole moment from the following: $$ CCl_4, NF_3, H_2S, HBr, SF_4, SiF_4, XeF_4, BeCl_2, SnCl_2, BrF_5, SO_2 $$

• A. \(5\)
• B. \(7\)
• C. \(6\)
• D. \(6\)

Hint:

A molecule is polar if it has an asymmetrical shape and polar bonds. Check molecular geometry and electronegativity differences to determine dipole moment.

Answer 1

The Correct Option is B

To determine the number of molecules having a permanent dipole moment from the given list, we need to analyze the molecular geometry and the electronegativity of atoms in each molecule. A molecule with an asymmetrical geometry will generally have a permanent dipole moment due to the uneven distribution of charges.

1. \(CCl_4\): Carbon tetrachloride has a tetrahedral geometry with four identical C-Cl bonds. The symmetry cancels out any dipole moments, making it non-polar.
2. \(NF_3\): Nitrogen trifluoride is a trigonal pyramidal molecule (similar to ammonia). The geometry is not symmetrical, resulting in a permanent dipole moment.
3. \(H_2S\): Hydrogen sulfide has a bent shape due to the two lone pairs on sulfur, making it polar with a permanent dipole moment.
4. \(HBr\): Hydrogen bromide is a diatomic molecule with a significant difference in electronegativity between hydrogen and bromine. It has a permanent dipole moment.
5. \(SF_4\): Sulfur tetrafluoride has a seesaw shape due to the presence of a lone pair on sulfur. This shape is asymmetrical, thus having a permanent dipole moment.
6. \(SiF_4\): Silicon tetrafluoride is a tetrahedral molecule with symmetrical Si-F bonds, and thus it is non-polar.
7. \(XeF_4\): Xenon tetrafluoride has a square planar geometry, resulting in the cancellation of dipole moments due to symmetry; therefore, it is non-polar.
8. \(BeCl_2\): Beryllium chloride is a linear molecule with symmetrical charges. The dipole moments cancel out, making it non-polar.
9. \(SnCl_2\): Tin(II) chloride has a bent geometry due to lone pairs, resulting in a permanent dipole moment.
10. \(BrF_5\): Bromine pentafluoride has a square pyramidal shape due to a lone pair, thus it is polar with a permanent dipole moment.
11. \(SO_2\): Sulfur dioxide has a bent shape causing asymmetrical distribution of electron density, leading to a permanent dipole moment.

Based on the analysis, the following molecules have a permanent dipole moment: \(NF_3\), \(H_2S\), \(HBr\), \(SF_4\), \(SnCl_2\), \(BrF_5\), and \(SO_2\). Therefore, the correct number of molecules having a permanent dipole moment is 7.