Destroyer Gen Chem (Polar and Non-P)

[ApexPredator]

2015 Destroyer Gen Chem Q# 64 and Q# 68.

From Q# 64 Destroyer has CBr4 as non-polar, then question #68 has CH2Cl2 as Tetrahedral polar. I'm confused as to why CBr4 is tetrahedral with no lone pairs and isn't considered polar. What am I missing here?

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[WolfsBane]

Since the CBr4 has to a Bromine pulling electrons in all 4 directions it has no dipole and is non polar while the CH2Cl2 has 2 Cl's pulling in one direction while 2 H's pull in the other direction. Since this is the case and since there is a difference in electronegativity there is a dipole and its going to be polar.

 

[WolfsBane]

Another helpful tip would be to count all valence electrons and draw out the structure.

 

[csulapredental]

2015 Destroyer Gen Chem Q# 64 and Q# 68.

From Q# 64 Destroyer has CBr4 as non-polar, then question #68 has CH2Cl2 as Tetrahedral polar. I'm confused as to why CBr4 is tetrahedral with no lone pairs and isn't considered polar. What am I missing here?

Anytime somethin has 4 of the same things coming off of it, it's non polar

 

[ApexPredator]

Since the CBr4 has to a Bromine pulling electrons in all 4 directions it has no dipole and is non polar while the CH2Cl2 has 2 Cl's pulling in one direction while 2 H's pull in the other direction. Since this is the case and since there is a difference in electronegativity there is a dipole and its going to be polar.

Thank you for the explanation

 

[DAT Destroyer]

2015 Destroyer Gen Chem Q# 64 and Q# 68.

From Q# 64 Destroyer has CBr4 as non-polar, then question #68 has CH2Cl2 as Tetrahedral polar. I'm confused as to why CBr4 is tetrahedral with no lone pairs and isn't considered polar. What am I missing here?

This is a VERY important question. CBr4 is NONPOLAR......the dipoles all cancel out. You have that straight ! OK...CH2Cl2 is tetrahedral....thus the dipoles do NOT cancel out. If you were to build a model, you would EASILY convince yourself of this. If it was planar...then yes...they would cancel...but not when tetrahedral. If you see 4 of the same groups on a methane...yes it is nonpolar...BUT this is NOT true for molecules like SF4, XeF4, etc. For species like these....we need to find out the total valence electrons and look for lone pairs. See Destroyer problems, I have shown this many times.

Hope this helps

Dr. Romano

 

[ApexPredator]

This is a VERY important question. CBr4 is NONPOLAR......the dipoles all cancel out. You have that straight ! OK...CH2Cl2 is tetrahedral....thus the dipoles do NOT cancel out. If you were to build a model, you would EASILY convince yourself of this. If it was planar...then yes...they would cancel...but not when tetrahedral. If you see 4 of the same groups on a methane...yes it is nonpolar...BUT this is NOT true for molecules like SF4, XeF4, etc. For species like these....we need to find out the total valence electrons and look for lone pairs. See Destroyer problems, I have shown this many times.

Hope this helps

Dr. Romano

Thank you for clearing this up for me

 

[DAT Destroyer]

Thank you for clearing this up for me

Always happy to help!