CHEMISTRY COMMUNITY

Porus_Karwa_2E

Homework questions and skimming over lecture notes always help me

Porus_Karwa_2E

k(1)/k' =K (equilibrium constant)
k' is the reverse or second process

Porus_Karwa_2E

We use q=mCdeltaT when mass is given in grams. q=nCdeltaT when moles are given

Porus_Karwa_2E

When graphing Kinetics what should we look for on the y-axis for the different orders. Also what units do we use for each

Porus_Karwa_2E

What exactly does Unique Rate Law mean?

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Normally, the problem will tell you what the rate determining reaction is.

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There is no curve, but Dr.Lavelle does adjust the grades a bit so everyone benefits.

Porus_Karwa_2E

k is the rate constant, K is the equilibrium constant

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We should get it back in section next week.

Porus_Karwa_2E

There are multiple methods, but deltaG=deltaH-TdeltaS is a powerful equation. Also, we can do G=-nFE

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I put in order of the reaction. So for Fe2+ to Fe3+ on the anode side would go in that order.
On the reduction (cathode) we would write in order Fe3+,Fe2+

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We can use it to solve for variables that might be unknown to us from the problem.

Porus_Karwa_2E

Gibbs free energy up to Friday's lecture

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I think Homework problems are the best indicator of what's going to be on the exam.

Porus_Karwa_2E

If the change in DeltaG is negative then the forward reaction will be spontaneous, but if deltaG is positive then the reverse reaction is spontaneous.

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Q: Why was the mole of oxygen molecules excited when he walked out of the singles bar?
A: He got Avogadro's number!

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Ka is equal to 10^-pka. Once you find the Ka value you can solve for [H+] using the reaction equation. From that we can find pH.
In other words, yes you're correct

Porus_Karwa_2E

Can someone please explain how to calculate the entropy through different phase changes using the heating curve as a guide?
Thanks!

Porus_Karwa_2E

The ideal gas laws go with PV=nRT where P is 1atm n is 1 mole of gas.

Porus_Karwa_2E

m^3 is equal to about 1000 L so you'd need to do the conversion of that to give you atm x L. 101.325 atmXL is equal to 1 joule. I believe this conversion is somewhere on the formula sheet for 14B.

Porus_Karwa_2E

The online modules might be able to help you understand concepts, but for study guides I would go to TA run review sessions since they typically show problems from past Midterms.

Porus_Karwa_2E

The formation of bonds is exothermic, thus we place a negative sign.

Porus_Karwa_2E

Our textbook uses bar mostly, but atm is technically the proper SI unite for pressure. Since there is only a 1% difference between bar and atm they are interchangeable though.

Porus_Karwa_2E

What exactly is delta U and what does the equation for it mean?

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When we are given questions on exams I believe everything we need to know will be provided to us.

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No they are not required but they are good practice

Porus_Karwa_2E

Yes, just add up the enthalpies of prods-reactants

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This does not effect solids or liquids

Porus_Karwa_2E

Karyn Nguyen 1K wrote:Will we be tested on concepts (like multiple choice or short answers) or will it just be math problems?

Based on what happened last quarter in 14A, Dr. Lavelle's style is having mostly math problems with a sprinkling of concept questions throughout the exam.

Porus_Karwa_2E

Changing the concentration doesn't change K because if we take out more reactants the equation will shift in order to make up for the deficient amount of reactants to make the K ratio the same.

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It is outline 1 with acids and bases

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Both are approximately the same thing, but atm is the SI unit for pressure so I'd put your answer in atm if not stated otherwise.

Porus_Karwa_2E

Solid and liquids don't have concentrations so no reaction would really occur

Porus_Karwa_2E

To add onto the above comment the X variable is much easier to use as after you are done assigning variables we would just need to use the quadratic equation.

Porus_Karwa_2E

The trend is that across (left to right) a group electronegativity increases and up a period it also increases.
I am unaware of any exceptions to this trend.

Porus_Karwa_2E

I just came out of a chem review session and I was told that on the exam we will have to order from most to least acidic, but they will never make it so that we must confirm an oxoacid with a non-oxoacid. It is always comparing oxoacids with oxoacids and non with non. Just know longer the atomic rad...

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Will this be on the chem14A final?

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If the central atom is not the same in a set of oxoacids then the molecule with the central atom with the highest electronegativity will be the most acidic. If the central atoms are the same for a group of oxoacids then we must see the number of Oxygens that are attached to the central atom. The mor...

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Yes the central atoms is always positively charged.

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No they do not. The only thing that matters is the areas of electron density.

Porus_Karwa_2E

3 pi bonds and 1 sigma bond means its a quadruple bond.

Porus_Karwa_2E

According to Dr. Lavelle, the test will be on Chapter 3 (3.12 6th edition) and all of chapter 4, but my TA and I believe other TA's did review content in their sections that is outside of this text (like Acids and Bases and Intermolecular forces). Will this additional content also be included on Tes...

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It is more stable in terms of formal charge like this. Plus this doesn't break the octet rule.

Porus_Karwa_2E

A double bond will count as one electron density so it doesn't affect the shape of the molecule.

Porus_Karwa_2E

Test 3 will be more conceptual based rather than calculations.

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The amount of lone pairs around the central atom also matters as in a T Shape there are 2 lone pairs on the central atom that makes the other atoms move over. On Trigonal Planer the lone pairs of the other atoms push eachother to make a triangle

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Well X is the number of possible bonds and E is the number of lone pairs. So you'd have to memorize this combination for each shape.

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Technically no you would just need to memorize the shapes and when each geometrical figure should be applied. I will admit though that the formula will definitely help.

Porus_Karwa_2E

More electronegative means that the element more greatly wants another electron to fill its octet.

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The increased bond length makes the bonds stronger.

Porus_Karwa_2E

We won't be required to draw a VSEPR model, but a tetrahedral model doesn't have any lone pairs as exhibited in CH4.

Porus_Karwa_2E

I got 130 pm because I took the average of the 140pm and 120pm.

Porus_Karwa_2E

The difficulty level should be comparable to the homework problems

Porus_Karwa_2E

Hi just confirming for the midterm we'll only have to be responsible for the configuration of all of the s-block, all the p-block, and just the first row of the d-block?

Porus_Karwa_2E

My TA wasn't particularly strict on SigFigs on Tests #1 and #2. Will it be more of a factor for the midterm?

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Both are 2 different things but the trend is the same.

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It is graded on completeness

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I believe that deltaP and deltaX are inversely proportional. A good rule of thumb is that variables on the same side of an equation are inversely proportional, while variables on different sides of an equation are directly proportion. For example, in p=mv, p and v are directly proportional (p and m ...

Porus_Karwa_2E

I believe the bond is stronger when there are more bonds. So in terms of energy needed to break the bonds single<double<triple. Also, interestingly, for the length of a bond the more bonds an atom has the shorter the bond. So a triple bond is shorter than a double bond and a double bond is shorter t...

Porus_Karwa_2E

During the lecture, Dr.Lavelle gave an example where n=2, l=1, and m=-1

From this, he told us this is an electron in 2px state. I don't exactly understand how he got the "x" from this information.

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For the exam, we will only need to go up to Quantum Numbers and Orbitals.

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Dr.Lavelle said that everything in Quantum World up to the information presented on Friday's lecture is what we will be tested on. In other words, the lecture from Friday is the cutoff.

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It is confirmed that we won't need to memorize any of them

Porus_Karwa_2E

The equation he gave in class is correct.

Porus_Karwa_2E

On the exam, we were supposed to box our answers, so I'm pretty sure that if you boxed the right answer it would negate the "doodles"

Porus_Karwa_2E

It would make sense to get our grades back next time we go into discussion yes.

Porus_Karwa_2E

I believe the syllabus does state that we won't know our grades until the end of the quarter since the class is set up on a bell curve of some sorts (only meant to help your grade).

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Is Chapter 1 homework due in our next discussion period or is it due on the one after that?

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All you have to do is count the atoms out for the molecular formula.

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Typically, yes we should just infer that we are supposed to use SI units

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Avogadro's number is pretty much just "things." So for instance, if you want to turn moles to molecules you'd multiply the moles you have by 6.022x10^23 molecules

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Remember we only have to do 7 problems from the hw list on the syllabus

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