Identify the molecule that has polar bonds but is non-polar (net dipole moment is 0)

a. CHCl3
b. NH3
c. BCl3
d. SCl2
e. H2S

The molecular geometry?

The last two are bent?, I believe. (d,e) Hydrogen can only make a single bond, right?

Um. The first has zero lone pairs and four bonds, so it's tetrahedral, maybe. (a)

I think the third is trigonal planar. (c)

And the second is.... uh, like one lone pair and three bonds. So, trigonal pyramidal, then.

OK. You know the shapes rather well. So a is tetrahedral; however, with 3 H and 1 Cl, it cannot be symmetrical so it will have a net dipole moment. NH3 is trigonal pyramidal (tetrahedral electronic geometry) so it will have 3 Hs and a lone pair so it will not be symmetrical and will have a net dipole moment. Following that line of reasoning, which do you think is symmetrical, which means no net dipole moment.

Since the first two are bent then they will have a dipole moment, also.

BCl3 has equally spaced bonds between its three, so that one would be symmetrical, meaning no dipole moment.

=]

Very good.

To determine whether a molecule is polar or non-polar, you need to consider both the polarity of the individual bonds within the molecule and the molecular geometry.

First, let's consider the polarity of the bonds in each of the given molecules:

a. CHCl3: This molecule has polar bonds. Chlorine is more electronegative than carbon, causing the bonds between the carbon and chlorine atoms to be polar.

b. NH3: This molecule has polar bonds. Nitrogen is more electronegative than hydrogen, causing the bonds between nitrogen and hydrogen atoms to be polar.

c. BCl3: This molecule has polar bonds. Chlorine is more electronegative than boron, causing the bonds between boron and chlorine atoms to be polar.

d. SCl2: This molecule has polar bonds. Chlorine is more electronegative than sulfur, causing the bonds between sulfur and chlorine atoms to be polar.

e. H2S: This molecule has polar bonds. Sulfur is more electronegative than hydrogen, causing the bonds between sulfur and hydrogen atoms to be polar.

Next, we need to consider the molecular geometry to determine the net dipole moment of the molecule. The net dipole moment is the vector sum of the dipole moments of all the bonds in the molecule.

a. CHCl3: The molecular geometry of CHCl3 is a tetrahedral shape. The dipole moments of the polar C-Cl bonds cancel each other out due to the symmetric arrangement of the chlorine atoms, resulting in a net dipole moment of 0. Therefore, CHCl3 is non-polar despite having polar bonds.

b. NH3: The molecular geometry of NH3 is a trigonal pyramidal shape. The dipole moments of the polar N-H bonds do not cancel out, resulting in a net dipole moment which is non-zero. Therefore, NH3 is polar.

c. BCl3: The molecular geometry of BCl3 is a trigonal planar shape. The dipole moments of the polar B-Cl bonds cancel each other out due to the symmetric arrangement of the chlorine atoms, resulting in a net dipole moment of 0. Therefore, BCl3 is non-polar despite having polar bonds.

d. SCl2: The molecular geometry of SCl2 is a bent shape. The dipole moments of the polar S-Cl bonds do not cancel out completely due to the bent shape, resulting in a net dipole moment which is non-zero. Therefore, SCl2 is polar.

e. H2S: The molecular geometry of H2S is a bent shape. The dipole moments of the polar S-H bonds do not cancel out completely due to the bent shape, resulting in a net dipole moment which is non-zero. Therefore, H2S is polar.

So, among the given options, the molecule that has polar bonds but is non-polar (net dipole moment is 0) is (a) CHCl3.

You want the molecule that is symmetrical in the 3 dimensional shape. Do you know the shapes of these molecules?