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Chemistry Question 124 – AP-EAMCET 2026

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Observe the following sets of molecules and identify the set in which all molecules have dipole moment

A molecule has a net dipole moment if it contains polar bonds and possesses an asymmetric molecular geometry such that the individual bond dipoles do not cancel out.

Step 1: Understand Dipole Moment Conditions✦ Active

A molecule possesses a net dipole moment if it has polar covalent bonds and an asymmetric molecular geometry. Polar bonds arise from a difference in electronegativity between the bonded atoms. Asymmetry can be due to lone pairs on the central atom or an uneven distribution of polar bonds around the central atom. Symmetrical molecules, even with polar bonds, can have zero net dipole moment if the individual bond dipoles cancel each other out.

💡 Teacher's Secret Hint

Remember that both bond polarity AND molecular geometry are crucial. A molecule can have polar bonds but zero dipole moment if its shape is highly symmetrical, like CO2 or CCl4.

Step 2: Analyze Each Molecule for Dipole Moment○ Expand

Let's analyze each molecule by determining its Lewis structure, VSEPR geometry, and then evaluating its bond polarity and overall molecular symmetry:

1. H2S: Bent shape (V-shaped) due to two lone pairs on sulfur. S-H bonds are polar. The geometry is asymmetric, so it has a dipole moment.

2. C6H6 (Benzene): Planar hexagonal structure. All C-C and C-H bonds are nonpolar or have very small bond dipoles that cancel out due to high symmetry. No dipole moment.

3. CO2: Linear geometry (sp hybridized carbon). C=O bonds are polar, but they are equal and opposite, canceling each other. No dipole moment.

4. H2O: Bent shape (V-shaped) due to two lone pairs on oxygen. O-H bonds are very polar. The geometry is asymmetric, so it has a dipole moment.

5. NH3: Trigonal pyramidal shape due to one lone pair on nitrogen. N-H bonds are polar. The geometry is asymmetric, so it has a dipole moment.

6. HCl: Linear diatomic molecule with a polar H-Cl bond. It has a dipole moment.

7. BeCl2: Linear geometry (sp hybridized beryllium). Be-Cl bonds are polar, but they are equal and opposite, canceling each other. No dipole moment.

8. CS2: Linear geometry (sp hybridized carbon). C=S bonds are polar, but they are equal and opposite, canceling each other. No dipole moment.

9. BBr3: Trigonal planar geometry (sp2 hybridized boron). B-Br bonds are polar, but due to perfect symmetry, the three bond dipoles cancel out. No dipole moment.

10. PbCl2: Bent geometry due to a lone pair on lead (Pb is in Group 14, similar to Sn and Ge, often having lone pairs in lower oxidation states). Pb-Cl bonds are polar. The geometry is asymmetric, so it has a dipole moment.

11. SnCl2: Bent geometry due to a lone pair on tin. Sn-Cl bonds are polar. The geometry is asymmetric, so it has a dipole moment.

12. HgCl2: Linear geometry (sp hybridized mercury). Hg-Cl bonds are polar, but they are equal and opposite, canceling each other. No dipole moment.

💡 Teacher's Secret Hint

For molecules with central atoms from Group 14 (like Sn, Pb) in +2 oxidation states, always consider the possibility of a lone pair on the central atom, which often leads to bent geometries and thus a dipole moment.

Step 3: Evaluate Each Option Set○ Expand

Now, let's check each option based on the analysis from Step 2:

Option 1: H2S (has dipole), C6H6 (no dipole), CO2 (no dipole). This set is incorrect.

Option 2: H2O (has dipole), NH3 (has dipole), HCl (has dipole). All molecules in this set have a dipole moment. This set is correct.

Option 3: BeCl2 (no dipole), CS2 (no dipole), BBr3 (no dipole). This set is incorrect.

Option 4: PbCl2 (has dipole), SnCl2 (has dipole), HgCl2 (no dipole). This set is incorrect.

Step 4: Identify the Correct Set○ Expand

Based on the evaluation, Option 2 is the only set where all molecules (H2O, NH3, HCl) possess a dipole moment.

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