Molecule - Polar or Non Polar?

In summary: The tetrahedral shape allows for the bond polarities to cancel out, resulting in a net dipole moment of zero.
  • #1
meganw
97
0

Homework Statement



Determine whether each of the following molecules is polar or nonpolar.
(Please note that lone pairs have been omitted for simplicity!)

H
I - C - I
H

Homework Equations



Electronegativity, Polarity, Dipole moments

The Attempt at a Solution



It seemed to me like the C and I have the same polarity so the net dipole would have been zero, but the answer says the molecule is Polar. Why?

Thanks for any help with the explanation! =)

-Megan
 
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  • #2
No, I is more electronegative than C because it is halogen.

Note that the molecule adopts a tetrahedral shape. Either way, the dipole moment will go from the in-between of 2 C-H bonds to the in-between of 2 C-I bonds
 
  • #3
I'm sorry I don't get the last part of what you said. Do you think you could explain? =)

Thanks!
 
  • #4
Read dichloromethane in http://dwb4.unl.edu/Chem/CHEM869E/CHEM869ELinks/www.uis.edu/7Etrammell/organic/introduction/polarity.htm
 
Last edited by a moderator:
  • #5
Great link! Also, I have another question:

1) H3COCH3 H3CCH2CH3

It says that the first one has the higher boiling point because of dipole forces. Is there some sort of greater dipole between the C and the O? It looks like it might cancel out though?

2) C2H5OH CH3OCH3

Here, would it be the second one, on account of a great mass, London Dispersion forces being the factor that increases the boiling point?

Thanks! I'm starting to get this I think! =)

-Megan
 
  • #6
And wait, doesn't it say that the tetrahedral would cancel out?

"Tetrachloromethane

The top image show the bond electron density and the bottom image the molecular dipole

m = 0 D"
 
  • #7
meganw said:
Great link! Also, I have another question:

1) H3COCH3 H3CCH2CH3

It says that the first one has the higher boiling point because of dipole forces. Is there some sort of greater dipole between the C and the O? It looks like it might cancel out though?

2) C2H5OH CH3OCH3

Here, would it be the second one, on account of a great mass, London Dispersion forces being the factor that increases the boiling point?

Thanks! I'm starting to get this I think! =)

-Megan

1) Yes, permanent dipole permanent dipole (H3COCH3) is stronger than London Dispersion force (H3CCH2CH3).

2) BP should be C2H5OH (stronger hydrogen bonding) > CH3OCH3 (pdpd)

meganw said:
And wait, doesn't it say that the tetrahedral would cancel out?

"Tetrachloromethane

The top image show the bond electron density and the bottom image the molecular dipole

m = 0 D"

Yes, CCl4 would be a non-polar molecule.
 

Related to Molecule - Polar or Non Polar?

What is a molecule?

A molecule is a group of two or more atoms that are chemically bonded together. These atoms can be from the same element or different elements.

What does "polar" or "nonpolar" mean in relation to a molecule?

Polarity refers to the distribution of electrical charge within a molecule. A polar molecule has an uneven distribution of charge, with one end being slightly positive and the other end slightly negative. A nonpolar molecule has an even distribution of charge and no separation of positive and negative ends.

How do you determine if a molecule is polar or nonpolar?

To determine the polarity of a molecule, you can consider the electronegativity of its atoms and the molecular geometry. If the difference in electronegativity between the atoms is significant and the molecule has a symmetrical shape, it is likely polar. If the difference in electronegativity is small and the molecule has a symmetrical shape, it is likely nonpolar.

What are some examples of polar molecules?

Some examples of polar molecules include water (H2O), ammonia (NH3), and hydrogen chloride (HCl).

Why is it important to know if a molecule is polar or nonpolar?

Knowing the polarity of a molecule is important in understanding its physical and chemical properties. For example, polar molecules tend to have higher boiling and melting points, are more soluble in polar solvents, and can participate in hydrogen bonding. Nonpolar molecules, on the other hand, tend to have lower melting and boiling points, are less soluble in polar solvents, and cannot participate in hydrogen bonding.

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