Multiple Choice
Which of the following best describes the polarity of the molecule HCl?
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13. Liquids, Solids & Intermolecular Forces
Molecular Polarity
Multiple Choice
Determine if phosphorus trihydride, PH3, is polar or nonpolar.
A
Polar
B
Nonpolar
C
Cannot be determined
Verified step by step guidance1
First, understand the concept of molecular polarity. A molecule is polar if it has a net dipole moment, which occurs when there is an uneven distribution of electron density across the molecule.
Examine the molecular geometry of phosphorus trihydride (PH3). Phosphorus trihydride has a central phosphorus atom bonded to three hydrogen atoms. The molecular geometry is trigonal pyramidal due to the presence of a lone pair on the phosphorus atom.
Consider the electronegativity of the atoms involved. Phosphorus is less electronegative than hydrogen, which means the electrons in the P-H bonds are pulled slightly towards the hydrogen atoms.
Analyze the symmetry of the molecule. The trigonal pyramidal shape is not symmetrical, which means the dipoles from the P-H bonds do not cancel out, resulting in a net dipole moment.
Conclude that due to the molecular geometry and the difference in electronegativity, PH3 is a polar molecule.
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