CHEMISTRY COMMUNITY

Julia Zahra

A spontaneous process has a negative delta g and a positive delta g indicates a non spontaneous process.

Julia Zahra

Look at the units you need/have.

Julia Zahra

The graph of 1/[A] vs Time will be linear.

Julia Zahra

I don't think so.

Julia Zahra

The sculpture garden is nice, there's no outlets though so you have to make sure your stuff is charged.

Julia Zahra

Textbook problems are usually helpful, especially because he puts some of the textbook problems on the exams.

Julia Zahra

I think usually it will be given or you can determine it if you are given the overall rate law.

Julia Zahra

I think it will be on respondus proctored via zoom like the midterms.

Julia Zahra

Yes the final is cumulative and the amount of each topic should represent how much time was spent on it.

Julia Zahra

k is the rate of the forward reaction and k' is the rate of the reverse reaction.

Julia Zahra

You need to look at the units to decide which one works the best.

Julia Zahra

I think its anode over cathode, but I could be wrong

Julia Zahra

Its on the constants sheet, its 96485 C/mol

Julia Zahra

they have different units, so you would use whichever has the units that correspond to what you are trying to find/what info you have.

Julia Zahra

its the amount of energy available to do work

Julia Zahra

Use the first one if the temp is non standard, so K doesn't equal 298

Julia Zahra

a reaction that where reduction(red) and oxidation(ox) is occurring.

Julia Zahra

Happy (very late) valentines day.

Julia Zahra

use same account, it is linked to your uid

Julia Zahra

Kc for concentrations, Kp for partial pressures, and K is the same it is just not specifying c or p.

Julia Zahra

at equilibrium the forward and reverse reactions are happening at the same rate so the free energy(G) is not changing.

Julia Zahra

the equation for entropy is S=Kln(W) and ln(1)=0 so that means 0 entropy.

Julia Zahra

ln is just a specific log, ln is log base e its just a shortcut for saying/calculating it.

Julia Zahra

yes, you can use the acronym oil rig, oxidation is loss, reduction is gain, so when something is oxidized it loses an electron and its ox number decreases and when it is reduced it gains an electron and its ox number increases

Julia Zahra

Yes temp in kelvin is important bc units have to be consistent throughout the reaction/problem.

Julia Zahra

enthalpy is the total energy of a system, but heat is the energy being transferred.

Julia Zahra

exo sounds like external, so heat is released.

Julia Zahra

deltaU is the chagne in internal energy of a system, it is equal to deltaH-p*deltaV in a system with constant pressure.

Julia Zahra

because the measured bond enthalpies are based on averages determined experimentally, so they vary molecule to molecule.

Julia Zahra

if its not specified assume standard conditions, so 25C

Julia Zahra

An open system is when a reaction can exchange matter and energy with its surroundings, like a reaction in an uncovered beaker.

Julia Zahra

W=-p deltaV is for an irreverisble reaction at a constant pressure, w=-nRTln(V1/V2) is for a quicker reversible reaction.

Julia Zahra

in an isolated system there is no energy or matter exchange with surroundings, in a closed system there is no matter exchange, but energy can still be transferred to and from the surroundings.

Julia Zahra

In a closed system energy can still be absorbed from the surroundings or released to the surroundings, but in an isolated system there will be insulation or something to prevent the exchange of energy with the surroundings.

Julia Zahra

If heat is required or delta h is positive then the reaction is endothermic, is heat is released or delta h is negative then the reaction is exothermic.

Julia Zahra

A change in K would not cause a shift left or right a change in Q might though.

Julia Zahra

If you flip or reverse the reaction the equilibrium constant is divided by 1. so 1/K

Julia Zahra

Yeah you can tell if a reaction is endo or exothermic because a -△H indicates a exothermic reaction, or one that releases energy, while a +△H value indicates an endothermic reaction or one that requires energy.

Julia Zahra

Molarity calculated by moles/Liter, and a molarity change is calculated with the equation (Molarity1)(Volume1)=(Molarity2)(Volume2), and you just solve for whatever the unknown variable is.

Julia Zahra

A lower pH means a more acidic solution so more H+ in the solution.

Julia Zahra

You should be able to determine what direction the reaction is going in, that will allow you to determine which side is +x and which is -x.

Julia Zahra

Its the amount a weak acid has dissociated it is [H+]/[HA]x100.

Julia Zahra

I believe its X.

Julia Zahra

yeah I think that is correct, Kp is partial pressures of gases and Kc is molar concentration of aqueous solutions.

Julia Zahra

They're concentration doesn't change in the reaction.

Julia Zahra

If k>q that means that q has more reactant than product, the excess reactant will cause the reaction to proceed in the forward direction to get rid of the excess reactant.

Julia Zahra

All things you listed except for the achieve hw are not graded and are technically optionally, though highly encouraged, he usually puts some of the textbook problems on exams so those can be helpful to do even though they aren't graded.

Julia Zahra

All things you listed except for the achieve hw are not graded and are technically optionally, though highly encouraged, he usually puts some of the textbook problems on exams so those can be helpful to do even though they aren't graded.

Julia Zahra

K is the ratio of reactant/product at equilibrium while Q is the same ratio at any point in the reaction.

Julia Zahra

Yes, there are no units because they all cancel out.

Julia Zahra

I think a ligand is just an atom with 1 or more lone pairs.

Julia Zahra

I believe en is ethylenediammine and edta is ethylenediaminetetraacetic acid

Julia Zahra

delocalized means it has resonance and the electrons are evenly distributed, localized means the electrons are in one spot and there are no resonance structures.

Julia Zahra

use periodic trends to determine which atoms are bigger or will have a stronger attraction.

Julia Zahra

Valence shell electron pair repulsion.

Julia Zahra

Because if a molecule has 6 bonds it probably has an octahedral shape.

Julia Zahra

It was on the hw so I think its fair game for the final.

Julia Zahra

Yeah its because a sigma bond can rotate and a pi bond cannot so it breaks easier.

Julia Zahra

If the dipole moments are symmetrical going in opposite directions and equal in strength they cancel out.

Julia Zahra

Cl is much further right so it is more electronegative

Julia Zahra

Yeah it ends up being CH4O

Julia Zahra

find the molecular formula from the masses

Julia Zahra

HBr is a stronger acid, it dissociates easier because the bond is longer/weaker.

Julia Zahra

Pi bonds are always weaker cause they can't move.

Julia Zahra

Julia Zahra

It just depends which atom is more stable with a charge other than 0

Julia Zahra

E is lone pairs AX is bonds

Julia Zahra

Thanks for sharing your methods. :)

Julia Zahra

yes i believe so

Julia Zahra

The final is content from the entire quarter

Julia Zahra

dipole dipole is between two already polar molecules, because they have dipoles already, induced dipole happens with non polar molecules that become temporarily polar.

Julia Zahra

Hydrogen can only form one bond to be the central atom it would have to be able to form more than one bond.

Julia Zahra

That must've been a mistake, because you should be adding them.

Julia Zahra

If there is a substantial difference in electronegativity in the elements in the molecule then the molecule is polar, unless there is symmetry then the dipoles kind of cancel out and the molecule becomes non polar.

Julia Zahra

Ionization energy is the energy required to remove one electron, the easiest to remove electron.

Julia Zahra

Al has more protons so there is a stronger attraction between the nucleus and electrons, so it has a higher first ionization energy than Na.

Julia Zahra

yeah, the stronger the bond, the shorter the bond because the attraction pulls the atoms closer together.

Julia Zahra

groups are the columns and periods are the rows.

Julia Zahra

each orbital can hold two electrons so for the s subshell since it can only hold 2 electrons it has one orbital, for p since it can have 6 electrons that's 3 orbitals.

Julia Zahra

I don't think there's a specific charge that needs to be lowered, but if you are able to get it closer to zero you should.

Julia Zahra

It can occur with the elements F, O, or N

Julia Zahra

When converting to different units I keep it with exponents if possible so it's more accurate, if not keep as many decimal places as possible until your final answer.

Julia Zahra

Lavelle hasn't mentioned anything about a curve so I don't think so.

Julia Zahra

Someone told me 4-5 days after the midterm.

Julia Zahra

I believe we are taking it in class so about 50 min, and I don't know if multiple choice or short answer, probably similar to the practice question he posted that he said would be on the midterm.

Julia Zahra

I think it means electrons need less energy to reach the 4d state than the 5s state.

Julia Zahra

Content taught through friday 10/15 is what we need to know for the midterm, that's what he said in lecture today.

Julia Zahra

I usually don't round if possible until I get the answer.

Julia Zahra

He said that content up through Friday(Today)s lecture could be on the midterm.

Julia Zahra

He provides us with a link to the constants and equations we need for exams on his website
https://lavelle.chem.ucla.edu/wp-conten ... ations.pdf use these numbers, I believe we are supposed to print it out ourselves to have with us for exams.

Julia Zahra

The equation only applies to moving objects, so if the velocity is 0 then the equation doesn't apply to that object.

Julia Zahra

This is the link to the periodic table that Lavelle provides on his website
https://lavelle.chem.ucla.edu/wp-conten ... _IUPAC.pdf

Julia Zahra

I believe they are the same, E=hv is probably just the equation for one photon and the other is an equation to find the energy of more than one photon.

Julia Zahra

You might be confusing frequency with wavelength, as the wavelength increases the frequency decreases, so since visible light has a shorter wavelength it has a higher frequency.

Julia Zahra

I don't know if there's any tricks other than just learning them over time, but I found at least for the prefixes like centi, milli, nano, etc it is helpful to know like the definitions of the prefixes.

Julia Zahra

For three there are only 2 sig figs, because you didn't put a decimal point at the end of the number.

Julia Zahra

I've found that doing the modules before the start of a new unit is helpful.

Julia Zahra

Yeah that's what I do too, helps also to write the units in each step of the equation so you don't mix anything up by accident.

Julia Zahra

The number of moles of individual elements must stay the same but not the number of moles of different molecules that have multiple elements.

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