Multiple Choice
Which one of the following molecules has a zero dipole moment?
13. Liquids, Solids & Intermolecular Forces
Molecular Polarity
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Which of the following molecules contains polar bonds but is overall non-polar?
A
CHCl3
B
H2O
C
CO2
D
NH3
Verified step by step guidance1
Step 1: Understand the difference between polar bonds and overall molecular polarity. A polar bond occurs when two atoms have different electronegativities, causing a dipole moment. Overall molecular polarity depends on both the polarity of individual bonds and the molecular geometry, which determines if dipoles cancel out or add up.
Step 2: Analyze each molecule's bonds for polarity by comparing electronegativities of the atoms involved. For example, in CO2, the C=O bonds are polar because oxygen is more electronegative than carbon.
Step 3: Examine the molecular geometry of each molecule to determine if the bond dipoles cancel out. CO2 has a linear shape, so the two polar C=O bonds are oriented 180° apart, causing their dipoles to cancel and making the molecule overall non-polar.
Step 4: Contrast this with other molecules: H2O has bent geometry causing dipoles to add up, NH3 has trigonal pyramidal shape with a net dipole, and CHCl3 has tetrahedral geometry but the different atoms create an overall dipole moment.
Step 5: Conclude that CO2 contains polar bonds but is overall non-polar due to its linear geometry causing dipole cancellation.
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