[FancySnow]

So the professor allow us to take home this quiz before the exam, but he hasn't post up the answers yet.

I have other classes to tend to so I was hoping to get the answers here. Don't worry, I have attemptted work on them already, but I just need someone to check my work and if I'm doing something wrong please lead me in the right direction.

I posted images as well for clarity.

OK, first molecule is H2NNH2.
-Both N atoms have 3 bonding pairs and 1 lone pair.
-Molecular shape is trigonal pyramidal
-Bond polarity for H-N is polar because ΔEN= 0.9. N-N is nonpolar because ΔEN = 0.
-Molecular Polarity is polar because shape is trigonal pyramidal. THIS IS WHAT I AM NOT SURE OF. HELP. I was thinking nonpolar because the two trigonal pyramidal from each nitrogen cancel each other out. But i look online and everyone say this molecule is polar. So, molecule polarity only dependent on molecular shape then?

Second molecule is IBr3Cl-1
-Iodine has 4 bonding pairs and 2 lone pairs
-Molecular Shape is square planar
-Bond polarity for I-Br is nonpolar because ΔEN = 0.3. I-Cl is polar because ΔEN is 0.5.
Molecular Polarity is nonpolar because of square planar shape. I'm not sure about this. I'm thinking it's polar because at one end, (the I-Cl) end, it is polar. So wouldn't that mean there's a slight polar pull on that end?

Help please.
1)


2)

[Enthalpy]

About hydrazine, drawing flat on paper won't help you. Try to imagine in 3D how it looks like, or build a model with plastic balls and sticks, or make a computer model with the proper software. Then, consider that the N-N bond can rotate. Do you see a polarization then?

[FancySnow]

About hydrazine, drawing flat on paper won't help you. Try to imagine in 3D how it looks like, or build a model with plastic balls and sticks, or make a computer model with the proper software. Then, consider that the N-N bond can rotate. Do you see a polarization then?

Can you help me draw it? LOL, I'm so confused with 3D drawing.

But, while you're at it, is the second one nonpolar despite I-Cl bond polar?

[Enthalpy]

I suppose you'll make more progress if you draw the 3D model of hydrazine by yourself. To go on with chemistry, you need to
- Have seen enough 3D models of molecules
- Train to imagine simple molecules without any material representation, and you should achieve this with hydrazine
- Know to use some means to make 3D models, be it software, plastic balls and sticks, something.

So right now would be a fantastic time to begin.

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About [IBr₃Cl]^-:
Would [IBr₄]^- be polar?
So is the polarity of each I-Br the only factor?