CHEMISTRY COMMUNITY

Bryan Chen 1H

yea memorize them

Bryan Chen 1H

probably similar to the midterm

Bryan Chen 1H

isothermal reversible expansion

Bryan Chen 1H

mine is available on myucla gradebook right now

Bryan Chen 1H

gibbs free energy!!!!

Bryan Chen 1H

the same pathway both ways

Bryan Chen 1H

i think one is more related to spontaneity and the other is more related to rate

Bryan Chen 1H

I remember my TA writing Ecell>0 than K>0 and vice versa, and you can prove this from the equations

Bryan Chen 1H

both should work

Bryan Chen 1H

yes, if you look at the rate constant and its units

Bryan Chen 1H

According to Khan Academy, "The reaction mechanism describes the sequence of elementary reactions that must occur to go from reactants to products."

Bryan Chen 1H

^ no matter how "fast" the fast one is the slowest one is always the determinant because each other reaction depends on it to also occur

Bryan Chen 1H

im assuming open book means like textbook notes lecture notes etc

Bryan Chen 1H

since mols are the same for each, I looked at volume of soln. where the delta temp change is greatest in the smallest volume. I thought of the soln volume like an absorbant, so the more water there is, the less a rxn will be able to shift its temp as compared to a little volume of water

Bryan Chen 1H

in these problems i tend to think of heat as a reactant (endothermic) or product (exothermic). Then depending on an increase or decrease in temp, I use le chatelier's principle treating heat as a R or P

Bryan Chen 1H

it depends on the unit of the gas constant. if its .08206 Latm/Kmol then use Kelvin, but another gas constant COULD have its units in celcius for whatever reason and then you should use celcius (but it probably will never ever come up in real life or a problem)

Bryan Chen 1H

yes, since they are made in one step and used up in the next they are not included in the overall final one

Bryan Chen 1H

positive E naught is equal to negative delta G meaning spontaneous

Bryan Chen 1H

you should use delta G = -RTlnK + RTlnQ.

Bryan Chen 1H

my TA during discussion says it's always safe to put Pt(s) as the electrode when there is no other metal to act as it

Bryan Chen 1H

i think all of electrochem and 2nd page thermodynamics so if its on the electrochem learning outcomes then yes

Bryan Chen 1H

Bryan Chen 1H

i would always use the equation sheet and look at the units, especially for constants. for example, .08206 = R, R has units in L, atm, K, and mol. So, on a test you should make sure when plugging into PV=nRT, for example, to match up those units to the R constant.

Bryan Chen 1H

It increases pressure, but it has no effect on the reaction because volume stays the same and therefore the concentrations of species also do

Bryan Chen 1H

oil rig
oxidation is loss
reduction is gain

Bryan Chen 1H

From the equation ∆G= ∆H-T∆S. ∆G= ∆H when the second term is close to 0. Therefore, you should find an equation with very little entropy change, which is often when the reactants and products are in the same state with the same amount of moles (best when all solid).

Bryan Chen 1H

i think because the pH of the stomach is so acidic and there are already so many H+ floating around that the high pKa of the compound (and the natural dissociation of it) is too weak to "compete" with the already established acidity

Bryan Chen 1H

i think 298 is 25+273 and 25 is considered "room temperature" not "standard"

Bryan Chen 1H

i believe they are the same, or at least you assume its always reversible

Bryan Chen 1H

ignore the solid since it is not apart of the K expression, and multiply the other two together to find Q.

Bryan Chen 1H

maybe there are exceptions but i think for this class and the midterms isothermal is always reversible

Bryan Chen 1H

irreversible expansion refers to a gas expanding against a constant external pressure. use the equation w= -Pex(deltaV)

Bryan Chen 1H

it just happens to be this way because of the math. its similar to how a higher pH is less H+ concentration, just like how higher pKa is weaker acid

Bryan Chen 1H

basically, deltaG depends on deltaH and deltaS to be a spontaneous(-) or nonspontaneous(+) rxn. Since it is a new topic i dont think we need to know much more than that

Bryan Chen 1H

typically, liquids occupy more space or are more disorderly than solids, and same for gas and liquids

Bryan Chen 1H

probably only the first page of outline 4

Bryan Chen 1H

yes im pretty sure

Bryan Chen 1H

i think q

Bryan Chen 1H

if u imagine an open beaker, the constant pressure will be the force of air pressure acting down on it from the environment

Bryan Chen 1H

i personally dont think about multiplying or dividing, i look at the units of each (kJ, and kJ/mole), and i try to format it so the units cancel. i think its called dimensional analysis or something

Bryan Chen 1H

i got mine back in discussion!

Bryan Chen 1H

steam has more energy than boiling water at the same temp

Bryan Chen 1H

No, strong acids and bases also have Ka and Kb i think, it is just very large (and they also dissociate completely) so there's no real need to use it in problems

Bryan Chen 1H

I'm pretty sure you can use partial pressures as well as concentration because partial pressures is based on the similar idea as concentration

Bryan Chen 1H

on the equations sheet look at the units for R and make sure they match up with those given in the problem, or those that you may convert to/use

Bryan Chen 1H

Yea I always check to see if K is small but if its around like 10 to -3 or -4, you can do the approximation but make sure to check if x is less than 5% of the initial concentration

Bryan Chen 1H

there requires a large heat of vaporization (delta H) change to convert water molecules from the liquid to gas phase, so steam has much more "energy" in it

Bryan Chen 1H

there's no set number that makes something definitely "weak" or "strong" i'd say but compared to strong acids like HCl, an acid that only dissociates 1 proton per 1000 other molecules is much weaker relatively speaking.

Bryan Chen 1H

it is an endergonic reaction i think so base your answer off delta H

Bryan Chen 1H

i suggest writing out the chemical reaction taking place and looking at the reactants side. If its like a base dissociating, then use kb, for example.

Bryan Chen 1H

i dont think you need to know how its derived but prof. jukka keranen teaches you how K is derived in his ls30A lecture if youre interested.

Bryan Chen 1H

yea, and then afterwards do the x value over initial concentration just to double check it is under 5%

Bryan Chen 1H

i think it would be 2 unless otherwise specified but im not too sure

Bryan Chen 1H

water is a pure liquid and a solvent. while it "takes part" in the reaction, the change is so small its negligible

Bryan Chen 1H

the pressure the gas above a liquid exerts down on it

Bryan Chen 1H

Usually if there are no products yet and only reactants, the reactants will decrease and the products will increase by a multiple of X depending on the co-efficients.

Bryan Chen 1H

K = equilibrium constant, K is the same for a given reaction at a given temperature. Q = reaction quotient, it is the ratio of P/R at any given moment during a reaction.

Bryan Chen 1H

Kc is when you use concentrations of reactants/products to calculate K and Kp is when you use the partial pressures of the gases

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