CHEMISTRY COMMUNITY

Lisa Werner 2F

what is the difference between adiabatic and isothermal?

Lisa Werner 2F

i have heard from past students that there is also a large portion based on thermodynamics.

Lisa Werner 2F

what is the conversion from atm to torr?

Lisa Werner 2F

conceptually, what does A mean in the arrhenius equation mean?

Lisa Werner 2F

lyndon said that we probably wouldn't have to know how to derive equations, but if it's on the syllabus it may appear on the test

Lisa Werner 2F

it means that q=0, so delta=w. it will usually be specified in the problem.

Lisa Werner 2F

thank you lyndon !!!

Lisa Werner 2F

yes, a porous disc is notated by a single line

Lisa Werner 2F

thank you so much karen! these worksheets were so helpful!

Lisa Werner 2F

in worksheet 5 problem 6, how do we know that work is 0?

Lisa Werner 2F

i think dr. lavelle said that he wouldn't make us do it because the math is too complicated.

Lisa Werner 2F

when is w=0 and when is q=0? what are the key words that indicate these two conditions?

Lisa Werner 2F

at different temperatures, ph 7 is not always neutral.

Lisa Werner 2F

what are scenarios/conditions where deltaU=0?

Lisa Werner 2F

it will be cumulative, but watch out for topics that have not yet been tested in class (kinetics)

Lisa Werner 2F

the actual concentration of A in first order reactions is exponentially decaying; however, we plot the y axis using ln, which gives us a linear graph with a slope

Lisa Werner 2F

molecularity is based upon the number of types of reactant molecules in a reaction

Lisa Werner 2F

the order of a reaction is equal to the sum of the powers of each term in the rate law. for example, if you had rate=[A]^2[B]^1[C]^3 then 2+1+3=6 so the order of the reaction described by that particular rate law would be 6

Lisa Werner 2F

when you find the two half reactions in the from of reductions from an original equation, whichever one has the reactants and product on the same side as the original is the cathode and the one where the reactants and products are flipped is the anode.

Lisa Werner 2F

Dr. Lavelle announced in lecture that the midterm average was an 80%.

Lisa Werner 2F

when lyndon posts his review worksheet, it will probably be announced in lecture.

Lisa Werner 2F

from my understanding: they both refer to the same equation; however, "the rate of consumption of ____" could change the sign. for example, if it is the rate of consumption of a reactant then it will be positive, but if it is the rate of consumption of a product then it will be negative.

Lisa Werner 2F

it is just a specific case of the gas law equation pv=nrt

Lisa Werner 2F

how can we tell when to use 3/2R and 5/2R as C?

Lisa Werner 2F

delta u is 0 when q=-w

Lisa Werner 2F

I believe everything in that lecture could be in it, except for the Gibbs free energy.

Lisa Werner 2F

You should do the calculations with kelvin.

Lisa Werner 2F

Do we have discussion on the day of the midterm?

Lisa Werner 2F

Also, I believe it can only be used for ideal gases.

Lisa Werner 2F

Dr. Lavelle explained it in lecture and it is required for several homework problems, so I think he considers it fair game for the midterm.

Lisa Werner 2F

Is there a conceptional reason as to why a reversible reaction does more work than a reversible one? The textbook gave the example of a reversible reaction occurring in a container with the same pressure inside and outside, making the system work against the equal pressure to expand. On the other ha...

Lisa Werner 2F

Bond enthalpy is the least accurate method because it based on the average enthalpies required to break a type of bond across all different types of molecules, rather than a specific molecule.

Lisa Werner 2F

Phase changes involving the breaking of bonds (solid->liquid->gas) are endothermic because they require/absorb heat. Phase changes involving the formation of bonds (gas->liquid->solid) are exothermic because the release heat.

Lisa Werner 2F

Technically speaking, I believe that any homework problems are accepted, but we should begin to work on the thermodynamics outline to stay up to date in the class.

Lisa Werner 2F

I noticed that one homework problem and one worksheet for this section had questions regarding polyprotic solutions, but I didn't think that they were covered in lecture. Does anyone know if they will be on Test 1 or not?

Lisa Werner 2F

K specifically describes the reaction at equilibrium, whereas Q can describe the reaction at any time.

Lisa Werner 2F

Pressure can be changed by changing the temperature or adding an inert gas without changing the volume.

Lisa Werner 2F

I am assuming that the test will include acids and bases because last quarter Dr. Lavelle tested everything covered in lecture up until the Friday before the test.

Lisa Werner 2F

It means that the reverse reaction is thermodynamically favored, so it is happening at a greater rate than the forward reaction.

Lisa Werner 2F

I recommend doing as many practice problems as possible by doing those from the book and attending workshops with practice handouts.

Lisa Werner 2F

Yes, you can assume Kp as essentially the only way to find the K of homogenous gas is through the partial pressure. Similarly, you can assume Kc when dealing with the K of homogenous aqueous reactions because you use molarity to find it.

Lisa Werner 2F

do we use the bis-, tris-, etc. if a ligand is a polydentate or if it has another greek prefix? basically does oxalate need them or not?

Lisa Werner 2F

If a molecule has many atoms with high polarizability, the LDF can actually be quite strong.

Lisa Werner 2F

Cl is more electronegative, making the electron density around the H atom less. Therefore, it can more easily be donated.

Lisa Werner 2F

In the textbook, it says if A (the element bonded to H) is more electronegative, then the acid will be stronger. However, this rule doesn't work considering between HF and HCl, F is more electronegative than Cl, but HF is a weaker acid than HCl. Why does the rule not apply?

Lisa Werner 2F

To expand from the previous reply, their concentrations are therefore interchangeable in the pH equation.

Lisa Werner 2F

London dispersion forces are intermolecular forces so they only affect how the molecule interacts with others, not affect bond strength.

Lisa Werner 2F

I think you also need to know that pH + pOH = 14.

Lisa Werner 2F

They are the same thing. Electron geometry would be when lone pairs are considered when determining shape, but it seems like this is almost never considered.

Lisa Werner 2F

We have to assume from the problem that the LDF of H2Se overwhelm that of H2S because Se has a higher polarizability than S, so it has stronger LDF.

Lisa Werner 2F

In regards to time, does anyone know if the final will have a similar amount of time allotted to each question as the midterm? Or will we have more time?

Lisa Werner 2F

There should be overlap if you are referring to the the diagram of the s hybridizing with the p orbital. If you are referring to the diagram of the bond between two atoms, there should not be overlap.

Lisa Werner 2F

When you give your answer you will always use the greater than or equal to sign, unless the question is asking for the minimum uncertainty.

Lisa Werner 2F

From my understanding, chelation occurs when a polydentate ligand bonds with a central metal in more than two places, creating a ring. Therefore, only polydentate ligands can be chelating.

Lisa Werner 2F

you can tell if a ligand is polydentate by looking at the figure and finding the places where it could bond to a central metal, considering the angles.for example, if a ligand could bond in two places, but they are on different side of the molecule, it is still monodentate.

Lisa Werner 2F

thank you so much!

Lisa Werner 2F

my TA said that the midterms will be handed out after lecture on Wednesday

Lisa Werner 2F

usually you do not have to write the formal charge of each atom for points unless instructed to do so, but it will help you find the correct lewis structure by demonstrating which structure will have the lowest energy.

Lisa Werner 2F

Also note that C,N,O and F all have exceptions to the trends!
in order from least to greatest in electronic affinity: N,C,O,F
in order from least to greatest in ionization energy: C,O,N,F

Lisa Werner 2F

I would assume that you should always include the brackets during the exam just to safe.

Lisa Werner 2F

Yes because it will determine where the double bond should go

Lisa Werner 2F

I don't think that there is limit. Either way, I think it is arbitrary because finding the lowest formal charge will keep you from ever getting close to what the limit would be, so I wouldn't worry about it.

Lisa Werner 2F

Thank you so much! This was really helpful!

Lisa Werner 2F

I believe it will be cumulative from the beginning of the course.

Lisa Werner 2F

More specifically, it determines the MINIMUM uncertainty of the position.

Lisa Werner 2F

Kg is used because it is the SI unit.

Lisa Werner 2F

I prefer taking hand-written notes in class, then going over them the next day and typing them on Google Docs. This is a good review and also ensures organization, clarity, makes it easier to find a specific subject later on.

Lisa Werner 2F

Thank you so much for this insight!

Lisa Werner 2F

My T.A. said that the deadline for the posts each week is Sunday night!

Lisa Werner 2F

My TA taught my discussion class that a good way to convert units is to simply substitute the power of 10 associated with the prefix for the prefix when doing calculations. For example, 1 mmol would become 1x10^-3mol.

Lisa Werner 2F

From my understanding, although the atomic weight, molecular weight, and formula weight are slightly different, they can all be found by finding the total weight of the atom(s) in a given atom, molecule, or formula. Therefore, the basic concept is the same.

Lisa Werner 2F

I have always been taught to round up numbers ending in 5 as well.

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