CHEMISTRY COMMUNITY

Hello All,
This is Lyndon Bui, one of your UA's. In preparation for your final this Sunday, I have attached several items.

First, here is a practice final covering material from after the midterm only. {Files no longer available}

Second, here is the practice midterm we distributed at a review session before the midterm. {Files no longer available}

Third, here are some of my past worksheets from my UA sessions. {Files no longer available}

NOTE: At my review session this Friday, CS24, 6-9PM, I will be going over the practice final first. With the extra time, we can go over pre-midterm material or any other questions you may have. Please print and complete the practice final before coming to the review session on Friday. For questions on any of the other worksheet/test questions I have posted, you can reply to this post and someone (me or other students) will answer you! Happy Studying:)

Hi,
Can you post the answers for the past two review worksheets for Week 7 and Week 9?

Hi,
Is there any way you could post the answers to the practice test for those people that are unable to come to the review session?
Thank you!

Hey!,

Can the solutions be posted for the final please! Thank you.

I do not have any formal solutions typed up; I only have the key that I wrote myself. Here are pictures in pdf form. This is the best I can do for giving solutions/answers.

Practice test solutions: {Files no longer available}

Week 7 worksheet solns: {Files no longer available}

Week 9 worksheet solns: {Files no longer available}
Number 1 has an error that I did not catch until it was recently brought to my attention. The question should read "...x is the equilibrium concentration of O2(g)" rather than SO2.

Good luck on all your finals!
-Lyndon

Thank you for this! However I thought LeChatelier's wasn't supposed to be on the test? Now I'm confused

allyz1F wrote:Thank you for this! However I thought LeChatelier's wasn't supposed to be on the test? Now I'm confused

LeChatelier's was covered in class and is on the outlines, so it will definitely be on the test. Please refer to course website for detailed outlines on what information you need to know. https://lavelle.chem.ucla.edu/wp-conten ... ibrium.pdf

On worksheet 7:
1. Would we be marked down for putting the concentrations in brackets? Never heard of this...
4. Why was en put before Iodide? I thought anionic ligands were supposed to be put before neutral when writing the formula?

on worksheet 9 number 1, the question says that x is the equilbrium concentration of so2. I understand that you have to balance the equation, but I don't understand equilbrium concentration would go from x to 2x when the question said that it should be x. Why is it that is is written as 2x instead?

On the back of the Practice Midterm, I was not sure how to do question 2. Its a 2 step reaction that produces hydrogen from methane and water. I got the correct answer by solving for the limiting reactant (CH4) of the first reaction and using that to solve for the amount of H2 produced in the first reaction. Then all I did was solve for H2 in the second reaction using the amount of CO produced in the first one. I got the answer right, however i was wondering if I was just lucky in assuming that CO would be the limiting reactant again for the second one. Can you assume this? or should I have found the amount of water left after the first reaction(which i wasnt sure how to do) and then used that to test to see if water was the limiting reactant of the second rxn, just to be sure?

Kayla Ikemiya 1H wrote:On worksheet 7:
1. Would we be marked down for putting the concentrations in brackets? Never heard of this...
4. Why was en put before Iodide? I thought anionic ligands were supposed to be put before neutral when writing the formula?

1. No, I do not think you would be marked down but I am not entirely sure.
4. We did not go over any rules in class about ligand order when given a name and asked to write the formula, so any order would work. But do be sure to write the name in alphabetical ligand order when given a formula.

AtreyiMitra1E wrote:on worksheet 9 number 1, the question says that x is the equilibrium concentration of so2. I understand that you have to balance the equation, but I don't understand equilibrium concentration would go from x to 2x when the question said that it should be x. Why is it that is written as 2x instead?

Number 1 has an error that I did not catch until it was recently brought to my attention. The question should read "...x is the equilibrium concentration of O2(g)" rather than SO2. Sorry about that one and good job paying attention.

-Lyndon

alyssawhite1L wrote:On the back of the Practice Midterm, I was not sure how to do question 2. Its a 2 step reaction that produces hydrogen from methane and water. I got the correct answer by solving for the limiting reactant (CH4) of the first reaction and using that to solve for the amount of H2 produced in the first reaction. Then all I did was solve for H2 in the second reaction using the amount of CO produced in the first one. I got the answer right, however i was wondering if I was just lucky in assuming that CO would be the limiting reactant again for the second one. Can you assume this? or should I have found the amount of water left after the first reaction(which i wasnt sure how to do) and then used that to test to see if water was the limiting reactant of the second rxn, just to be sure?

You should have used the amount of water left over from the first reaction. However much CH4 was used is equal the amount of H20 used up. Remaining water is used in the second step with the CO that is produced.
-L

Is MO theory going to be on the final? It's in the course reader and I've seen a few questions asked about it on Chem Community.

for Week 9, problem 6c, why does expansion favor products?

Thank you for the worksheets and practice exams! Is there any way I could get the answers to the first practice midterm?

There is a question on the final practice test, number 22, that asks how many O2 molecules can myoglobin bind and how many myoglobins form a hemoglobin. I know biologically the answer is each myoglobin can bind one oxygen and hemoglobin is composed of 4 myoglobins, but what is the chemical explanation to how you know (or how you can figure out) it can bind one oxygen and why 4 would form a hemoglobin?

I remember Lyndon stating that while the explanation is more complicated, a simple way to think about it is that the molecule will tend to favor an octahedral structure (the most common structure for coordinate complexes) with a coordinate number of 6. Since the complex is currently at a coordinate number of 4, a protein attaching to form myoglobin will make the number 5. Therefore, 1 O2 can be attached to make the number 6.

Timothy Kim 1F wrote:for Week 9, problem 6c, why does expansion favor products?

I also have this question. It seems like there are two moles on each side of the reaction.

The moles of iodine is in a solid state, so it wouldn't be included when determining which side has more moles of gas.

Michelle Pham_3H wrote:The moles of iodine is in a solid state, so it wouldn't be included when determining which side has more moles of gas.

thanks!