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Topic: Electrochemistry Homework Answers Check Request  (Read 1712 times)

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Offline keyag

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Electrochemistry Homework Answers Check Request
« on: March 30, 2024, 04:56:10 PM »
Dear Chemical Forums,

I hope you are doing wonderful.

I have finished my electrochemistry homework and am wondering if you can please check my work before I go to submit it. I have attached images of the 5 provided questions and my respective answers (highlighted in yellow).

Thanks in advance for your help.

Offline mjc123

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Re: Electrochemistry Homework Answers Check Request
« Reply #1 on: March 30, 2024, 06:10:49 PM »
1. Write a balanced equation for the cell reaction (always the first thing you should do). What are the exponents of the concentrations in Q?
2. E° is the standard cell potential, not electrode potential. What would E° be if both concentrations were the same?
3. ΔG° should be in kJ/mol, but if the question gets it wrong, what can you do?
4 & 5 - haven't checked calculations, but method looks correct.

Offline keyag

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Re: Electrochemistry Homework Answers Check Request
« Reply #2 on: March 31, 2024, 04:21:00 PM »
1. Write a balanced equation for the cell reaction (always the first thing you should do). What are the exponents of the concentrations in Q?
2. E° is the standard cell potential, not electrode potential. What would E° be if both concentrations were the same?
3. ΔG° should be in kJ/mol, but if the question gets it wrong, what can you do?
4 & 5 - haven't checked calculations, but method looks correct.

Dear mjc123, I thank you very much for your help. My revised results with your helpful feedback are shown in the attached images. Concerning your point relating to question 3: given that the Faraday constant is in coulombs per mole, and E°_cell is in volts, the results will be in joules per mole (J/mol). But in the hypothetical situation where the question gets it wrong, I could convert it to kJ/mol by dividing my result by 1000.

Thank you for checking my questions 1-5, mjc123. If you could please let me know if my new calculations/work are correct and if I would be good to submit, I would much appreciate it. Thank you in advance!


Offline mjc123

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Re: Electrochemistry Homework Answers Check Request
« Reply #3 on: April 01, 2024, 08:52:15 AM »
I haven't checked the calculations in detail, but the methods look right. However, for part 2 there are a couple of errors in writing the equation.
E = E° - RT/nF ln([Ag+]R/[Ag+]L)
You have written log rather than ln (but seem to have done the calculation correctly), and have used [Ag+]L/[Ag+]R, which would give you a negative answer. Be careful.

Offline keyag

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Re: Electrochemistry Homework Answers Check Request
« Reply #4 on: April 02, 2024, 08:33:09 PM »
I haven't checked the calculations in detail, but the methods look right. However, for part 2 there are a couple of errors in writing the equation.
E = E° - RT/nF ln([Ag+]R/[Ag+]L)
You have written log rather than ln (but seem to have done the calculation correctly), and have used [Ag+]L/[Ag+]R, which would give you a negative answer. Be careful.

Thank you very much for your checking, mjc123! Good spot with log vs. ln! I had meant to put in ln. Regarding the negative, mjc123, I have adjusted it to be 1.0 on top and 5.71 on the bottom. Thank you for spotting this as well. The ultimate expression is attached as a screenshot.

In your opinion, mjc123, this means then that every answer that I have seems correct, right? Thank you for your help. Once I get this final approval from you, I will go ahead and submit since I will be confident of my results. Thank you in advance for your assistance.

Offline mjc123

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Re: Electrochemistry Homework Answers Check Request
« Reply #5 on: April 03, 2024, 02:50:45 PM »
As I say, I haven't checked all the calculations, but the methods look correct.

Just being pedantic, I would have a quibble with Q4 where they ask you to express a number greater than two million to 2 decimal places. I assume they mean "when expressed in scientific notation", as you have done. But still, it would have been better to say "to 3 significant figures".

Offline keyag

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Re: Electrochemistry Homework Answers Check Request
« Reply #6 on: April 06, 2024, 07:37:23 PM »
As I say, I haven't checked all the calculations, but the methods look correct.

Just being pedantic, I would have a quibble with Q4 where they ask you to express a number greater than two million to 2 decimal places. I assume they mean "when expressed in scientific notation", as you have done. But still, it would have been better to say "to 3 significant figures".

Thanks for your help, mjc123! I got full points! As to why that is the case, my professor told me it is because of the platform in which the questions are administered (it has issues with sig figs or something like that). In any case, thank you very much for your time and assistance!

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