Page 2 of 2

Posted: Tue Nov 27, 2018 8:58 pm
Why does LiCl exhibit greater ionic character than LiBr?

Posted: Thu Nov 29, 2018 1:51 am
On Worksheet 6, #1 it asks to draw the most stable lewis structure for nitrogen dioxide (NO2), to determine the shape, and determine whether or not it it polar. In the key, the lewis structure is drawn with one single bond between nitrogen and oxygen and one double bond between nitrogen and the other oxygen atom and one single lone electron on nitrogen - this results in a formal charge of +1 on nitrogen and -1 on the oxygen that is bonded by a single bond. Wouldn't the most stable lewis structure be one with no formal charges at all, such as when both oxygens are double bonded to the nitrogen and with a single lone electron on the nitrogen?

Posted: Fri Nov 30, 2018 2:16 pm
Hello students!

Hope everyone had lots of good food and caught up on sleep over Thanksgiving! Below you will find this Sunday's session worksheet attached. Since your final is on the Sunday before finals week, this week will unfortunately be the last peer learning session with me :'( (Unless you're taking 14B with Dr. Lavelle again!!) Anyways, we will finish reviewing the rest of the concepts of the course (coordination compounds and acids/bases) so there are quite a lot to cover this weekend.

Hope to see you all at the last session!

-Karen

Posted: Fri Nov 30, 2018 8:49 pm
Joussie Camacho 4I wrote:On Worksheet 6, #1 it asks to draw the most stable lewis structure for nitrogen dioxide (NO2), to determine the shape, and determine whether or not it it polar. In the key, the lewis structure is drawn with one single bond between nitrogen and oxygen and one double bond between nitrogen and the other oxygen atom and one single lone electron on nitrogen - this results in a formal charge of +1 on nitrogen and -1 on the oxygen that is bonded by a single bond. Wouldn't the most stable lewis structure be one with no formal charges at all, such as when both oxygens are double bonded to the nitrogen and with a single lone electron on the nitrogen?

If the structure is drawn with 2 double bonds and a single lone electron, the entire molecule has a +1 charge, but the question asks for a neutral NO2.

Posted: Fri Nov 30, 2018 8:52 pm
Isabel Nakoud 4D wrote:Why does LiCl exhibit greater ionic character than LiBr?

Cl is smaller and is more electronegative than Br, so it will attract electrons better towards itself, leading to greater separation of charge, thus, greater ionic character.

Posted: Fri Nov 30, 2018 9:53 pm
Are these worksheets based on the homework and test problems directly or are they independent?

Posted: Sat Dec 01, 2018 3:33 pm
Chem_Mod wrote:
Joussie Camacho 4I wrote:On Worksheet 6, #1 it asks to draw the most stable lewis structure for nitrogen dioxide (NO2), to determine the shape, and determine whether or not it it polar. In the key, the lewis structure is drawn with one single bond between nitrogen and oxygen and one double bond between nitrogen and the other oxygen atom and one single lone electron on nitrogen - this results in a formal charge of +1 on nitrogen and -1 on the oxygen that is bonded by a single bond. Wouldn't the most stable lewis structure be one with no formal charges at all, such as when both oxygens are double bonded to the nitrogen and with a single lone electron on the nitrogen?

If the structure is drawn with 2 double bonds and a single lone electron, the entire molecule has a +1 charge, but the question asks for a neutral NO2.

Where is the overall +1 charge coming from? Isn't the formal charge on nitrogen 0 when it's double bonded to each oxygen? (5 valence electrons - 5 (4 from double bonds and 1 from the one electron))

Posted: Sun Dec 02, 2018 3:45 pm
Is there no worksheet 8 for this weeks workshop?

Posted: Sun Dec 02, 2018 7:49 pm
So there wasn't a worksheet?

Posted: Mon Dec 03, 2018 11:51 am
Hi, are you going to post a final review packet? Thanks!

Posted: Mon Dec 03, 2018 2:35 pm
Here is the answer key to the very last worksheet! There is no worksheet 8 because no session was held during week 8 due to thanksgiving break.

For #4 on the acids and bases section, see if this helps: [img]
Screen%20Shot%202018-12-03%20at%202.27.37%20PM.png
[/img]

IMPORTANT******: NAMING of coordination compounds WILL be on your final exam. I apologize for the confusion. IN ADDITION, you will need to know how to calculate the pH of STRONG ACIDS AND BASES. pH = -log[H+] and pOH = -log [OH-]. pH + pOH = 14. Sorry I am still adjusting to the new curriculum change.

There will be additional review sessions hosted by TAs and other UAs this week so utilize them if needed! I highly suggest going to a review session on coordination compounds if you still have trouble with that topic (definitely my personal weaker topic). I won't be holding a comprehensive review session so this worksheet will be the LAST one for this quarter. You can review my past 9 worksheets to make sure you still remember how to do problems from older material.

Good luck on finals and happy holidays!!!!

All the best,
Karen Leung

Posted: Mon Dec 03, 2018 2:55 pm
Im just wondering why the tail has a -1 charge since for me when I calculated the formal charges of the nitrogens connected to Co I got +1, +1, +1, +1, and 0
Wouldnt that give an overall +4 charge for the tail?

Posted: Mon Dec 03, 2018 8:45 pm
Hi! Thank you for the workshop and answering all of my burning questions this quarter. I appreciate it!

Posted: Mon Dec 03, 2018 8:45 pm
Hi! Thank you for the workshop and answering all of my burning questions this quarter. I appreciate it!

Posted: Mon Dec 03, 2018 11:42 pm
How do you go about doing #3 in the acid/base section?

Posted: Tue Dec 04, 2018 9:56 am
Hi, is there a worksheet for this past weekend? Thank you!

Posted: Tue Dec 04, 2018 9:58 am

Posted: Wed Dec 05, 2018 2:06 pm
Angela Cordova 3F wrote:These worksheets have helped me so much on the tests, will there be any covering the topics for Test 3?

Worksheets 6 and 7 above pretty much cover the same topics that Test 3 did!

Posted: Wed Dec 05, 2018 4:55 pm
thank you this was very helpful!

Posted: Wed Dec 05, 2018 6:20 pm
Does anyone know how to do 2B please on ws 9

Posted: Thu Dec 06, 2018 10:59 am
Kenan Kherallah 1A wrote:Im just wondering why the tail has a -1 charge since for me when I calculated the formal charges of the nitrogens connected to Co I got +1, +1, +1, +1, and 0
Wouldnt that give an overall +4 charge for the tail?

I also have the same confusion can some explain please?

Posted: Thu Dec 06, 2018 11:00 am
Leela_Mohan3L wrote:How do you go about doing #3 in the acid/base section?

Yes, can someone explain how to solve #3 on the second page of worksheet 9 please?

Posted: Thu Dec 06, 2018 12:07 pm
On Worksheet 9, question #6, why would acid 2 be stronger than acid 4?

Posted: Thu Dec 06, 2018 6:17 pm
Thank you for the worksheets

Posted: Thu Dec 06, 2018 10:06 pm
will there be more worksheets for the recently covered material like acids and bases and coordination compounds ? Thanks

Posted: Thu Dec 06, 2018 10:31 pm
Carissa Young 1C wrote:will there be more worksheets for the recently covered material like acids and bases and coordination compounds ? Thanks

I think this last worksheet was the last one since our final is on Sunday when there would normally be a session

Posted: Fri Dec 07, 2018 3:53 pm
For Week 9 worksheet #5, why cant H3O+ and H2O neutralize an added base? And why cant H2O neutralize an acid and be potentially amphoteric?

Posted: Sat Dec 08, 2018 10:21 am
Kenan Kherallah 1A wrote:Im just wondering why the tail has a -1 charge since for me when I calculated the formal charges of the nitrogens connected to Co I got +1, +1, +1, +1, and 0
Wouldnt that give an overall +4 charge for the tail?

For the tail itself, you need to think about it when it's removed from the Co, so break the bond and give it its respective lone pairs, the charge should be 0 + 0 + 0 +0 + -1 = -1.
Leela_Mohan3L wrote:How do you go about doing #3 in the acid/base section?

The question tells you that you start with HB+, and not HB, and you also know that B is a weak base. Thus, you need to write an equation that turns HB+ into B. Then, since B is a weak base, we know HB+ is a weak acid, and from there we need to think about what acids do and what bases do. What ions do acids release and what constitutes a base?

annabel 1F wrote:For Week 9 worksheet #5, why cant H3O+ and H2O neutralize an added base? And why cant H2O neutralize an acid and be potentially amphoteric?

Technically it can, but I was looking for something less obvious and related to the bicarbonate buffering system. On the exam, you may want to avoid writing down the too obvious answers for problems like these.

Posted: Sat Dec 08, 2018 10:23 am
Karishma_1G wrote:On Worksheet 9, question #6, why would acid 2 be stronger than acid 4?

The CH3 groups in acid 4 has electron donating properties, which deems it a stronger acid by the electronegativity trend.

Posted: Sat Dec 08, 2018 10:23 am
Karishma_1G wrote:On Worksheet 9, question #6, why would acid 2 be stronger than acid 4?

The CH3 groups in acid 4 has electron donating properties, which deems it a stronger acid by the electronegativity trend.

Posted: Sat Dec 08, 2018 2:58 pm
Thank you for your help this quarter!

Posted: Sat Dec 08, 2018 3:22 pm
Chem_Mod wrote: For the tail itself, you need to think about it when it's removed from the Co, so break the bond and give it its respective lone pairs, the charge should be 0 + 0 + 0 +0 + -1 = -1.

For the N with formal charge -1, can you please explain why is it -1 instead of +1? When it's removed from the Co, it should be bonded with two other atoms, and have a lone pair. Is it because there is another lone pair that is not shown?
Thank you so much! :-)

Posted: Sat Dec 08, 2018 3:53 pm
Thanks Karen for the helpful worksheets!