Multiple Choice
Which of the following compounds contains a polar covalent bond?
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13. Liquids, Solids & Intermolecular Forces
Molecular Polarity
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Which of the following structural formulas represents a polar molecule?
A
CCl_4
B
H_2O
C
CO_2
D
CH_4
Verified step by step guidance1
Step 1: Understand that molecular polarity depends on both the polarity of individual bonds and the geometry of the molecule. A molecule is polar if it has a net dipole moment, meaning the bond dipoles do not cancel out.
Step 2: Analyze the molecular geometry of each molecule: CCl_4 and CH_4 have a tetrahedral shape, CO_2 is linear, and H_2O has a bent shape due to lone pairs on oxygen.
Step 3: Consider the electronegativity differences: C-Cl, C-H, C-O, and O-H bonds have different polarities. For example, O-H bonds are quite polar, while C-H bonds are less polar.
Step 4: Evaluate if the molecular geometry allows bond dipoles to cancel. In CCl_4 and CH_4, the symmetrical tetrahedral shape causes dipoles to cancel, making them nonpolar. In CO_2, the linear shape causes the two polar C=O bonds to cancel out.
Step 5: Recognize that H_2O has a bent shape, so the polar O-H bonds do not cancel, resulting in a net dipole moment, making H_2O a polar molecule.
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