Exam tonight...

Exam 3 is tonight so we spent most of class reviewing.  On little bit that we (sort of) added...  When calculating the heat of reaction for an aqueous process, it is sometimes easier to use the net ionic equation.  There aren't always tabulated values available for every soluble salt, but the ions can be found for most elements.

See you tonight, 6pm in SL104.

emailed question...

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Hello Dr.Bodwin,

I have been studying up on the Exams that you have on your page and some of them have some things that we didn't go over in class and I was just wondering if those things would still be on our exam. The things that I am wondering about is like the quantum numbers, electron configuration, and the wavelength problems. 
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We'll be getting to that material after this exam, don't worry about it for now.

Old exam keys...

Looks like I haven't had time to put a key together for a while...

http://msumgenchem.blogspot.com/2010/10/old-exam-keys.html

Question

Question from email:
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Dr. Bodwin,

I am wondering if the test on Monday will have material from our last exam and the new material covered since then or just the enthalpy??
Thanks

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A few people have asked me this question and the best answer I can give is "yes".  Although there will not be any questions that are strictly "exam 2 questions" on this exam, you will have to know how to do things from exam 2 to answer exam 3 questions.  If you are trying to calculate the heat liberated or absorbed by a reaction, you will have to be able to write a balanced equation.  If you're trying to write a balanced equation, you will have to be able to write balanced formulas.  Many enthalpy problems are the same as all the stoichiometry problems we looked at for exam 2, the only difference is that instead of calculating grams or molarity or volume, you'll be calculating heat.  You may need to determine the limiting reagent, or percent yield, just like any other stoichiometry problem.

Other questions, let me know.

Heat, heat, heat...

Today we went through some more enthalpy/heat transfer problems.  We also went through a problem that demonstrated Hess' Law; for a multi-step process, the sum of the enthalpies for all the steps should equal the enthalpy of the whole process.  We've actually been using Hess' Law the whole time we've been looking at enthalpy, but we didn't formally call it Hess' Law.

If you have questions, email me.  I have a few other things going on this weekend, but I will do my best to post answers to the blog ASAP.  If you need to take Monday's exam at an alternate time and have not yet talked to me, please check in either by email or in person before Monday.

And most importantly, take a break or two over the weekend.  The weather is supposed to be quite nice, so take a little walk around the block for a study break.  Volleyball is home tonight and tomorrow and football is home this weekend.

Enthalpy

Wednesday in class we went through a couple more enthalpy problems/calculations.  Enthalpy of formation values are tabulated and refer to the heat transfer when 1 mol of the substance is produced from its standard state elements.  The magnitude of that heat transfer is the same whether a substance is being formed from its elements or the elements are being formed from the substance, only the direction of the heat transfer (and therefore the sign of {delta}H) changes.  This is the key to calculating enthalpy of reaction using tabulated enthalpy of formation values.

Tonight at 6pm in HA113, Tri-Beta will be hosting research night.  Faculty from Biosciences, Chemistry, and Physics will give brief descriptions of their research and be available for questions.  If you're interested in doing research, this is a good opportunity to see a variety of the projects taking place on campus.

New OWL

Oh, and there are new OWL assignments posted.  Enjoy.

Enthalpy - the heat of a process

Today we linked heat capacity to the larger idea of enthalpy.  Enthalpy is the heat transfer associated with a chemical reaction or physical process.  We'll work through a few more examples on Wednesday.

The Exam

We spent most of today going over the exam.  Exam 3 will cover a LOT of the same material, so make sure that you use your performance on Exam 2 to guide you toward the areas you need to study more.  Having graded the exam, I can identify polyatomic ions as the biggest problem most people had.  There's no real trick for polyatomic ions, you just have to memorize them.  As with anything (music, language, sports, etc), the more you practice the more automatic a thing becomes.  When you write out the formula for nitrate 100 times while you're studying, you will tend to remember the formula for nitrate.

We also did a quick heat capacity problem at the end of class, we'll get more into that next week.  Keep an eye on the schedule, Exam 3 is a week from Monday, so it's coming up quickly.  Have a good weekend.

Volleyball tonight - Diggin for a Cure!

Tonight the MSUM volleyball team will be Diggin for a Cure to raise funds for and awareness of cancer research and treatment.  Come out and support Dragon Volleyball as they crush the Golden Eagles of UMinn-Crookston.

Exam Results

Exam 2 is graded, I'll give it back in class tomorrow.  The scores were not good.  A few people did quite well, but many did very poorly leading to an average just under 50%.  We'll spend some time talking about this tomorrow in class.

With renewed vigor...

Today in class we started looking at thermochemistry, the ways that heat and chemical processes interact.  This is a small part of the larger field of thermodynamics.  We looked at some of the foundational energy things (types, units, transfer) and just got to heat capacity.  On Friday we'll get exams back and dig a little deeper into heat capacity.

Exam 2 results

OK, not exactly results, I haven't graded the exam yet, but it seems like a lot of people struggled with this exam.  This is typically the most challenging material in Gen Chem I so it's not unusual for this exam to have lower scores.  I've posted a poll, let me know if you've identified specific problems in your approach to class.  The poll is 100% anonymous and is not monitored or moderated in any way, so it's not definitive scientific data, but if there's a consistent problem identified I might be able to do some things to help.

EXAM TONIGHT

Don't forget that we are in a different room and a different building for the exam this evening.  We will be in CB111, the Center for Business.

Chem Club Tutoring Schedule

I've posted the Chem Club Tutoring schedule in a panel to the left (<-- that way <--).  Take advantage of this service and let me (or them) know what's working or not working with the schedule or tutors.

Monday's in-class problem

I'll get answers posted for Monday's in-class problem some time today or tomorrow.