Test 2
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Test 2
Can someone provide some important concepts to keep in mind for test 2? I have the memory of a goldfish and I really want to do well on this test. Thank you!
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Re: Test 2
I know the bonds (sigma and pi), molecular shapes, bond angles and the intermolecular forces will be on test 2. I'm not sure if that is all though.
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Re: Test 2
I think you are also supposed to know the VSEPR Model, dipole moments and how that is related to polarity, the strength of different intermolecular forces. Anything that is on Homework 3F and 2E may be on the test.
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Re: Test 2
Kristina Rizo 3K wrote:I know the bonds (sigma and pi), molecular shapes, bond angles and the intermolecular forces will be on test 2. I'm not sure if that is all though.
Do you know if we will be expected to memorize the bond angles?
I thought he mentioned in lecture that we weren't but maybe I didn't listen correctly.
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Re: Test 2
Cassandra_1K wrote:Does anyone have any advice for remembering molecular shape?
Hi Cassandra,
I think it's good to start by remembering molecular geometry, where lone pairs are counted as regions of electron density. If there are 2 areas of electron density, the shape is linear and the angle 180 degrees. If there are three areas of electron density, the shape is trigonal planar and has 120 degree angles. If there are four, it is tetrahedral and has 109.5 degree angles. Five is trigonal bipyramidal, which has a mix of 120 and 90 degree angles. Finally, six is octahedral, which has 90 degree bond angles.
After you memorize these main forms, you can consider molecular shape. For this, lone pairs are not counted as regions of electron density, but they still influence shape. There're quite a lot, so I'll only provide a few examples. A molecule with configuration AX2E would be bent and have an angle close to 120 (slightly less because of the repulsion of lone pairs). A molecule with configuration AX4E would be see-saw shaped and have angles around 90 and 120 degrees. I've attached a chart that's been very useful to me, which contains visual representations and bond angles for all molecular shapes. I hope this helps!
-Rebecca
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Re: Test 2
Definitely know intermolecular forces (dipole moments) and the concept and shapes from the VSEPR model. Good luck! :)
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Re: Test 2
Rebecca Remple 1J wrote:Cassandra_1K wrote:Does anyone have any advice for remembering molecular shape?
Hi Cassandra,
I think it's good to start by remembering molecular geometry, where lone pairs are counted as regions of electron density. If there are 2 areas of electron density, the shape is linear and the angle 180 degrees. If there are three areas of electron density, the shape is trigonal planar and has 120 degree angles. If there are four, it is tetrahedral and has 109.5 degree angles. Five is trigonal bipyramidal, which has a mix of 120 and 90 degree angles. Finally, six is octahedral, which has 90 degree bond angles.
After you memorize these main forms, you can consider molecular shape. For this, lone pairs are not counted as regions of electron density, but they still influence shape. There're quite a lot, so I'll only provide a few examples. A molecule with configuration AX2E would be bent and have an angle close to 120 (slightly less because of the repulsion of lone pairs). A molecule with configuration AX4E would be see-saw shaped and have angles around 90 and 120 degrees. I've attached a chart that's been very useful to me, which contains visual representations and bond angles for all molecular shapes. I hope this helps!
-Rebecca
thank you so much for this chart
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Re: Test 2
knowing bond angles of vsepr structures and how lone pairs can affect those bond angles is probably a good idea
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Re: Test 2
I just did a bunch of the book problems from that section, and I also watched a youtube on intermolecular forces that had a lot of practice problems in it that I did while following along.
Re: Test 2
In regards to studying intermolecular forces, I would say the best way is to read the chapter in the book about them and then do practice problems.
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Re: Test 2
Cassandra_1K wrote:Does anyone have any advice for remembering molecular shape?
I memorized the AX formula that went along with the shape.
Re: Test 2
Will we need to know how to draw/know the shape of a molecule with more than one central atom?
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Re: Test 2
VSEPR shapes, intermolecular forces+ how they relate to boiling point, sigma and pi bonds...
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