Which of the following is the most polar compound?

[Toothguy80]

BF3
CF4
CBr4
CH2Cl2
CH2Br2

I have absolutely no idea about this one, they all look non polar to me.

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[issa]

BF3
CF4
CBr4
CH2Cl2
CH2Br2

I have absolutely no idea about this one, they all look non polar to me.

BF3 looks more polar.

 

[Toothguy80]

Please explain why one is polar and the others are not

 

[Decan]

BF3 looks more polar.

I disagree. The first 3 choices are symmetrical and thus, have no dipole moments (but they do have polar bonds). I say its CH2Cl2 because it is not symmetrical (the two hydrogens are less electronegative so the chlorine atoms will pull more electrons. CH2Br2 is also polar but not as polar as CH2Cl2 b/c Cl is more electronegative than Br.

 

[pharoh]

i agree with decan....
they have no di-pole moment so it has to be d.
i also belive that kaplan explains that i think i remember seeing it before

 

[dentistin2011]

no dipole moment in sp2

 

[ucla2134]

BF3
CF4
CBr4
CH2Cl2
CH2Br2

I have absolutely no idea about this one, they all look non polar to me.

It all come down to dipole moment. The polar molecule must have dipole bonds and the molecule with dipole bonds sometime cannot be polar if their vector cancel.
I think this stuff kinda involved in physics since you have to add vector and then you will compare the combination vector with the other vector present. if they are on the same side you have dipole moment. If they are on the opposite side you cancel them out. This eliminate BF3, CF4,CBR4
Tricky part: At first i think the BF3 is polar too but when you adding the two vectors which is on opposite side of the other vectors so they cancel out.
CL has higher electronegativity than Br so therefore it has the higher polar bond than BR

Remember that C-H does not have dipole moment, it is simply the nonpolar covalent bond

 

[Toothguy80]

and CH2Cl2 is the correct answer in Kaplan.

thanks

 

[albodent]

its in the back of the book