CHEMISTRY COMMUNITY

josephperez_2C

In electrochemistry, the equation is deltaG = -nFE, and n is equal to the change in electrons in the redox half reactions.

josephperez_2C

kB is Boltzmann's constant and is provided on the equations sheet. (1.38 * 10^-23 J/K)

josephperez_2C

"Delta n as in moles" would be the change in moles from there reactant to product side. For the combustion reaction CH4 + 2O2 > 2H2O + CO2, delta n would be negative 2 because water is a liquid.

josephperez_2C

Just making sure, n could never equal 0 since there is always a transfer of electrons right?

josephperez_2C

We have the equation deltaG = -nFEcell. For galvanic cells, the reaction is spontaneous and therefore Ecell must be positive because deltaG is negative. Not sure if this was a bit roundabout but that's how I think of it.

josephperez_2C

How do we determine intermediates in a reaction?

josephperez_2C

I believe you can use the 0.05916V equation when the temperature is at 25 degrees C. Just remember q would equal 10^((-n(E-E))/0.05916) since its log.

josephperez_2C

Hello guys. Can anyone help me find a practice problem in the book where we are given conditions for an integrated rate problem (ln[A] vs time gives a straight line) and we have to fint the order? Or something of that nature? I remember a problem in class but I can’t find one in the book that’s quit...

josephperez_2C

chemical equilibrium will be on the final exam as it covers everything we have covered in class so far

josephperez_2C

first, second, and zero order reactions have linear plots

josephperez_2C

temperature effects the rate constant

josephperez_2C

You add OH- in a basic solution to the side of the reaction that has less hydrogen accordingly.

josephperez_2C

Kinetics relates to how quickly a reaction reaches equilibrium while Thermodynamics relates to the energy stored in a reaction.

josephperez_2C

K is not constant per reaction because it fluctuates wit temperature.

josephperez_2C

Number of electrons transferred, it signifies whether or not the system is gaining or losing energy.

josephperez_2C

If the question gives certain values per mol then you know to use kJ/mol.

josephperez_2C

Know entropy and enthalpy as well because there a lot of questions that encompass those as well as GFE.

josephperez_2C

I believe the negative delta g that we typically see when deaing with gases is due to the fact that the entire process is spontaneous.

josephperez_2C

It is extensive because its magnitude is dependent on the amount of a substance in a given thermodynamic state

josephperez_2C

In 14A we received them about a week after we took it after lecture.

josephperez_2C

the internal energy of a system is the energy within the system, of the entire system, as well as the potential energy of the system as a whole due to external force fields

josephperez_2C

When heat is absorbed from the solution q for the solution has a negative value
When heat is absorbed by the solution, q for the solution has a positive value

josephperez_2C

ΔH°= standard enthalpy change
ΔH°r = standard enthalpy change of reaction
ΔH°f = standard enthalpy change of formation
ΔH°c = the standard enthalpy change of combustion

josephperez_2C

A system which can interchange mass and energy is considered an open system. A cup of tea is susceptible to the environment.

josephperez_2C

State functions are "variables" that define the state of a system

josephperez_2C

V=(Abase)(H)=A*D

josephperez_2C

Increasing the partial pressure of a reactant shifts reactions towards the products, decreasing the partial pressure of a reactants shifts the reactions towards the reactants.

josephperez_2C

Hess's law basically states that enthalpy changes are additive. Enthalpy change at each step of a multi-step reaction can be added to give Total Enthalpy Change.

josephperez_2C

I think it was just important to know that the constant V (calorimetry) is associated with it. The problems will say something like "In a constant P calorimeter," so I doubt we'll have to know exactly how it works.

josephperez_2C

Someone explained it to me like this: the energy required for water to go from a liquid to a gas is called the heat of vaporization, and when steam hits your skin, a lot of energy will be released as it condenses into a liquid

josephperez_2C

q(v) is heat at constant volume and q(p) is heat at constant pressure

josephperez_2C

In my experience the best way to prepare for professor Lavelle's exams is the practice problems that are assigned. It might sound a bit arbitrary but what I like to do is actually repeat and quickly jot down the steps to each problem after I've completed it. It's worked well for me and I also think ...

josephperez_2C

It is considered an approximation because deviations from ideal gas behavior are small.

josephperez_2C

We can come to certain conclusions that are more obvious, such as H2 -> 2H being endothermic, because H2 has lower energy than the 2 H's. However, because we are given more complex chemical reactions, it's not always possible.

josephperez_2C

They mean the same thing but I believe we will be more likely to see percent ionization on a test.

josephperez_2C

Yes. I believe you can use ICE tables if asked to find equilibrium partial pressures.

josephperez_2C

I always make sure to take really good notes in class because while it sounds trivial, lecture is probably one the best resources for doing well on the exams. Also one tip for navigating chem community is going into Quicklinks on the top left and clicking on active topics to respond to questions.

josephperez_2C

I believe we can use either but I know my TA said that since the textbook uses bar so would she. Just make sure you know that they are pretty much equal

josephperez_2C

^ you can refer to that chart and also Lyndon Bui mentioned that we should know cisplatin because Lavelle mentioned it in class. It's used to treat cancers.

josephperez_2C

Polydentate simply means ligands with more than one bonded atom. I believe you can just look at the amount of bonds, so an atom with 4 bonds is tetradentate for example.

josephperez_2C

It is a strong acid because it loses an H+. It's equation of dissociation is HBr(aq) -> H+(aq) + Br-(aq).

josephperez_2C

Li+ is the smallest cation and also has one less shell than Mg2+

josephperez_2C

They are the same and you can write it in both ways.

josephperez_2C

I believe it is 2NO2 + H2O -> HNO2 +HNO3

josephperez_2C

There is no such thing as a dumb question. It is spelled ammine.

josephperez_2C

Yes I remember my TA going over this in section.

josephperez_2C

Yes this is just a rule. For example sulfate is SO42−.

josephperez_2C

Each lone pair is considered a region of electron density so they should be taken into account.

josephperez_2C

I am mostly studying my notes and going over practice problems. I think it really helps to compare notes with other students to see if you missed anything.

josephperez_2C

The final will be cumulative with an emphasis on the later topics.

josephperez_2C

'Quick links' top left -> 'your posts'

josephperez_2C

They are all polar.

josephperez_2C

I think the case might be that not every lecture is on the same pace but I could be wrong. From Friday's lecture at noon, he said that we were ahead of schedule and that we would have no class on Wednesday.

josephperez_2C

The next test is week 9 in section. It might also have some chemical bond material because its needed for molecular structures.

josephperez_2C

Lewis structures are the only thing we need to know how to draw in the context of 14a I believe.

josephperez_2C

Hydrogen bonds are considered one of the stronger intermolecular attractions, but they are still weaker than covalent and ionic bonds.

josephperez_2C

^simply the way the orbitals are shaped determines the amount of electrons it can hold

josephperez_2C

Lone pairs at the central atom repel shared pairs of electrons and make bond angles varied

josephperez_2C

I'm going over notes from discussion and practice problems from the book. Also the review sessions are really helpful and I know there are some tomorrow!

josephperez_2C

Some unit conversions are given on the equation sheet, such as 1 nm = 10-9 m, so I would just review the ones that aren't on the worksheet.

josephperez_2C

On the midterms review session schedule, it says that it will be all material covered in Fundamentals, Quantum, Bonding to end of 3.11 (6 Ed.) and to end of 2C (7 Ed.).

josephperez_2C

The octet rule applies to most atoms, but there are exceptions like hydrogen.

josephperez_2C

It won't be a large amount of points taken off but yes you should have the correct amount of sig figs to get full credit. Some questions even have 1 sig fig in them.

josephperez_2C

I believe he said to choose the atom with the lowest ionization energy.

josephperez_2C

While there are some units on the equation sheet given, it is probably best to know units as best you can.

josephperez_2C

The formula sheet that was given on the first test is the same one that will be given on the second test and third test as well.

josephperez_2C

Joules is the correct unit.

josephperez_2C

It usually helps me to look at the entire equation and see if any atoms are already balanced and then balance the others accordingly.

josephperez_2C

A non-programmable calculator is allowed on exams.

josephperez_2C

You should use the amount of significant figures in your answer that corresponds with the least amount of significant figures in any one given value of the problem.

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