Multiple Choice
How many of the following molecules are polar: BrCl_3, CS_2, SiF_4, SO_3?
13. Liquids, Solids & Intermolecular Forces
Molecular Polarity
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How many of the following molecules are polar: PCl_5, COS, XeO_3, SeBr_2?
A
4
B
1
C
3
D
2
Verified step by step guidance1
Step 1: Determine the molecular geometry of each molecule using VSEPR theory. For example, PCl_5 has a trigonal bipyramidal shape, COS is linear, XeO_3 is trigonal pyramidal, and SeBr_2 is bent or angular.
Step 2: Analyze the symmetry of each molecule's shape. Symmetrical molecules tend to be nonpolar because the bond dipoles cancel out, while asymmetrical molecules are often polar.
Step 3: Consider the electronegativity differences between the central atom and surrounding atoms to identify bond dipoles. For instance, in PCl_5, the P-Cl bonds are polar, but the symmetrical shape cancels the dipoles.
Step 4: Evaluate the net dipole moment for each molecule by combining the bond dipoles vectorially. Molecules like COS (linear but with different atoms) and XeO_3 (trigonal pyramidal with lone pairs) will have a net dipole moment, indicating polarity.
Step 5: Count how many molecules have a net dipole moment (are polar) based on the above analysis. This will give the number of polar molecules among PCl_5, COS, XeO_3, and SeBr_2.
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