Which of the following molecules have dipole moments? (Select allthat apply.) (a) CH2Cl2 CHCl3 CCl4 (b) N2O CO2 (c) NH3 PH3 For the molecules that are polar, indicate the polarity of eachbond and the direction of the net dipole moment of the molecule
The Correct Answer and Explanation is :
Let’s evaluate the polarity and dipole moments of each molecule.
(a) CH2Cl2, CHCl3, CCl4
- CH2Cl2 (Dichloromethane): This molecule has two hydrogen atoms and two chlorine atoms bonded to a central carbon. Chlorine is more electronegative than hydrogen, creating dipoles between the carbon-hydrogen and carbon-chlorine bonds. The molecular geometry is tetrahedral, and due to the unequal distribution of electronegativity between the H and Cl atoms, CH2Cl2 is polar. The net dipole moment is directed towards the chlorine atoms.
- CHCl3 (Chloroform): Similar to CH2Cl2, chloroform has three chlorine atoms bonded to the central carbon. Chlorine’s electronegativity creates dipoles, and with a tetrahedral geometry, the molecule is polar. The net dipole moment is directed towards the chlorine atoms.
- CCl4 (Carbon tetrachloride): In contrast to CH2Cl2 and CHCl3, CCl4 has a symmetrical tetrahedral structure with four chlorine atoms. Although individual bonds are polar, the symmetry of the molecule causes the dipoles to cancel out. Therefore, CCl4 is nonpolar.
(b) N2O, CO2
- N2O (Nitrous oxide): Nitrous oxide has a linear structure, with nitrogen atoms at each end and an oxygen atom in the middle. Nitrogen and oxygen have different electronegativities, leading to bond dipoles. The geometry of N2O makes the dipoles not cancel out, so N2O is polar.
- CO2 (Carbon dioxide): CO2 has a linear geometry, and although the carbon-oxygen bonds are polar, the molecule is symmetrical. This symmetry causes the bond dipoles to cancel out, making CO2 nonpolar.
(c) NH3, PH3
- NH3 (Ammonia): NH3 has a trigonal pyramidal shape, with nitrogen at the apex and three hydrogen atoms at the base. Nitrogen is more electronegative than hydrogen, creating a net dipole moment that points towards nitrogen. Therefore, NH3 is polar.
- PH3 (Phosphine): PH3 has a similar geometry to NH3, but the electronegativity difference between phosphorus and hydrogen is much smaller, resulting in very weak dipoles. This makes PH3 almost nonpolar, though it can still have a very weak dipole moment.
Conclusion
The molecules that have dipole moments are:
- CH2Cl2
- CHCl3
- N2O
- NH3
The following molecules do not have dipole moments:
- CCl4
- CO2
- PH3
Image of the dipole moments for the polar molecules:
I’ll generate an image illustrating the dipole moments of the polar molecules CH2Cl2, CHCl3, N2O, and NH3.
Here is the illustration showing the dipole moments for the polar molecules: CH2Cl2, CHCl3, N2O, and NH3. The arrows indicate the direction of the net dipole moments based on the more electronegative atoms (Cl, O, N) in each molecule. Let me know if you need further clarification!
