Workshop Last Week

I should have probably done this before the exam last week, but maybe this will help someone for the final.

So, last week's workshop was all about orbitals in atoms with more than one electron. Here are the main points:

• Sub-orbitals (s,p,d,f) only differ in energy in atoms with more than one electron. When the sub-orbitals in an orbital (n=1,2,3...) all have the same energy, the atom is called degenerate.
  
• s, p, d, and f is the ording of sub-orbitals from lowest to highest energy.
• Only one emission line is observed on a spectrum of a degenarate atom (like hydrogen) when its electrons jump one energy levels. In non-degenarate atoms, mutiple lines are observed because of the fact that sub-levels (l) must change by + or - in the transition of an electron.
  
• Shielding refers to the fact that the core electrons in mutiple-electron atoms shield the atom's valence electrons from the full nuclear charge. Shielding is what makes multiple-electron atoms not degenerate.
• Periodic trends: ionization energy increases from left to right across a period and decreases top to bottom down a group. The opposite is true for atomic radius.
  

Thats it!

Exam Question Workshop 8

A common thing for teens in Rural WNY to do on dull midsummer days is to blow 2L bottles up. They do this in a non-neferious kind of way, in their open fields. They take a soda bottle and fill it with The Works Toilet Bowl Cleaner, then add balls of Aluminum Foil, cap it off, shake it and run. This reaction can easily explode large pumpkins and has the equation:

NaOH + Al --> Al(OH)3 + Na2O + H2

This reaction is performed at 24C and through your laboratory experiment the Activation Energy was determined to be 48kJ/mol. If these teens wanted to carry this reaction out at 8 times the rate, what would the Temperature have to be?

Figuring out E* at different pH's of water

There was one exam problem in which it asked you to calculate the E* of 2H+ + 2e- --> H20 at pH of 5. Will this type of problem be on the test, and if so what is the basic way to solve this problem.

Workshop post

sorry for the late post but here it is:

Oxidizing agent is in Cathode. Reducing agent is in Anode.

Negative ions (such as NO3-) leave salt bridge to the ANODE to prevent build up of positive charge (which would stop the system)

Positive ions (such as K+) leave salt bridge to the Cathode to prevent build up of negative charge (which would stop the system)

Electrons flow from anode to cathode.

finally (i know its been saiid but its important): REDUCTION POTENTIAL IS THE ABILITY OF SOMETHING TO BE REDUCED!!!!!!!!! HIGHER REDUCTION POTENTIAL WILL OXIDIZE ANYTHING WITH A LOWER REDUCTION POTENTIAL. IT IS A REALLY GOOD OXIDIZING AGENT. (and vice versa for a high oxidation potential).

Workshop 5 notes!

oxidizing agent- is being reduced, looses electrons + charge
reducing agent- gets oxidized, gains electrons - charge

If reduction potential is high, there is a higher potential to get reduced. They are also good oxidizing agents

If reduction potential is low, it will reduce anything and it will get oxidized

Ecell= Ecathode - Eanode

Chemistry Chapter 10 exam question

For ammonia (NH3) the enthalpy of fusion is 5.65 kJ/mol and the entropy of fusion is 28.9 j/kmol.
a. will the NH3 spontaneously melt at 200 K?
b. What is the approximate melting point of ammonia?


Question 47 from chapter 10.

Workshop #3 Fun

Ok, so here’s some fun information we learned today:

*Equations
∆S_universe = ∆S_system + ∆S_surroundings

a) Reversible:
∆S = q_rev/t_f = (nC∆T)/t_f

b) Irreversible:
∆S = n C ln(T_f/T_i) = n R ln(V_f/V_i)

*For entropy changes: (like in the exploration in the workshop)
If the surroundings don't really change temperature, the process will be reversible. (exp. a(I))
If the surroundings do change temperature noticeably, the process will be irreversible. (a(II))
The same goes for the system. (the iron piece)
(The wonderful example of the millionaire vs. the college student with $50)

*Entropy is independent of path of process
There will be the same amount of entropy transferred if it goes back and forth randomly before it reaches the final, or if it goes directly to the final entropy.
(It doesn't matter how you get to the final point, just as long as you get there.)

Week #2 Notes

Hey everyone,

I hope these notes help you out:

* A carnot cycle is the most efficient way heat can be converted to work. It is ideal and never actually occurs in real life because of friction and the loss of heat to the environment. The cycle is composed of two isothermal (no temp. change) and two adiabatic (no heat flow) reversible processes. These processes are either expansions (Won is negative) or compressions (Won is positive).

* A reversible process is one that can be reversed because it is ideal and none of the energy or heat involved is mistakenly lost forever due to friction and loss of heat to the environment. Reversible process never actually occur in real life.

* The efficiency of a carnot cycle is measured with the equation: efficiency = 1 - (Tlow/Thigh).

* Remember that all of the equations D-Rock wrote on the board should be used for engines. When you have a refrigerator problem, you should use these (I hope these are right):
- AB... Won = -qAB = nRTln(VA/VB)
- BC... Won = -qBC = Cv (Thigh - Tlow)
- CD... -Won = qDC = nRTln(VC/VD)
-DA... -Won = qDA = Cv (Tlow - Thigh)

* Work is always measured in terms of the work done on the system by the surroundings while heat is always measured in terms of heat gained by the system from the surroundings.

* Heat flows spontaneously from high to low temperature areas. If you want to make heat flow from low to high (like with a refrigerator), work needs to be done on the system.

Week #1 Highlights

Basically, to recap what we talked about in workshop last week:

-Laws of thermodynamics are broken down into the "system" and its "surroundings"

-The First Law of Thermodynamics states that internal energy for a system is the sum of heat absorbed by the system, and work done on the system (ΔE=q+w)

-Changes in a thermodynamic state happen when processes occur between the system and the surroundings.

Notes from workshop 1

First, our icebreaker.

We're all underclassmen
We're all sceince-y
We're all in freshmen housing
We're all on facebook
We're all jealous that it's 77 degrees in California.

Now the meat of the workshop

Work done on the system + heat absorbed on the system, is the 1st law of thermodynamics.

ΔE=q+w

In an exothermic reaction the system will lose energy but temperature will rise, because your thermometer measures the released heat.

If work is done by system, the heat is negative (there is a loss of heat) Imagine exercising, you lose heat through your skin.

ΔH=q under constant pressure

Hess' law
ΣΔH(total) = ΣΔH(products) - ΣΔH(reactants)

q=mCΔT

Exam Question 1

Sorry this is a little late, technology hates me!

(a). How much heat is evolved when 1 mole of propane is burned?
(b). What is the enthalpy of combustion per gram of propane?

Hf (CO2(g)) = -394kJ
Hf (H2O(l)) = -286 kJ
Hf (C3H8(g)) = -104kJ

Monday/Wednesday - Quiz # 1

I wanted to post the correct answer to this weeks quiz and explain it, so i am currently doing so...

the question was...

The combustion of XXXXXX liberates heat. Which of the following statements is true?
A) ΔH(reaction) > 0, ΔH(surroundings) > 0
B) ΔH(reaction) <> 0
C) ΔH(reaction) > 0, ΔH(surroundings) <>0.
D) something i cant remember.

The answer is B - I had a really good explanation, but somehow, it got erased, so when I get a second - ill put it back up
If there are any questions, please speak up - i know this can be somewhat confusing with all the signs and stuff, as it was(and still is) for me.

to quote someone who was probably important or succeeded somehow in life:

"The only stupid question is the one that goes unasked."

i actually just made that version up, but its very, very, very pertinent given our situation. Its actually just an all - around good quote that can be applied to life in general, given any situation. Keep that in mind.

Workshop # 1

Well kids (I call everyone kids - even people who are much larger than me), we made it through our first workshop. Thanks for everyone's cooperation, I think we are going to have a grand ol' time this semester. I'm sorry if the last part went a little fast - if you have any questions, pleaseeee either post to this blog or email me, your book, the professor, your high school chemistry teacher, your weird uncle who knows way more chemistry than he needs to i dont care - just get it answered. Also! if you find yourself reading someone else's question, and you have the answer.... POST back! help each other out - know what im sayin' ?? Check back here often, as i will most likely use the blog to get in touch with you guys - OK! see ya soon.

In the Beginning

Well well well, nice of you to join the party. And by party I mean Chemistry 132. This is the greatest class EVER, and if you don't agree, I will fight you.1 I'm Derek, your TA. I'll be helping you out this semester, and im really looking forward to working with each and every one of you.2 I hope the semester has started off nicely for you! Please, this blog is for you, so abuse it! Feel free to post any questions, comments or insights you may be having at the time of publication. Im looking forward to having a great semester with ya'll.3


1 I have never once fought someone, ever. (assume this to be a trend)
2 That was a very vague, blanket statement meant to make you feel good inside. By no means is it a personal insight, as I dont know a single one of you. I can assert, however, that by the time you are reading this I will have met you (or soon will) and will have a strong desire to get to know you and make your wildest chemistry dreams come true. (This is a sincerely genuine comment)
3 I reside in the state of New York, which is in the northeastern United States, where is is very rare, if not wrong, to use the phrase "ya'll". I may or may not continue using it. Because I'm a rebel. I also say "pop"-all the time.