CHEMISTRY COMMUNITY

Abigail_Hagen2G

Since an intermediate cancels out, you wouldn't write it in the final balanced equation.

Abigail_Hagen2G

And since the units for reaction rates are always molarity/ time, this will help you find out the k units.

Abigail_Hagen2G

It's probably wouldn't occur without a catalyst.

Abigail_Hagen2G

Kinetics is all about the rate. It involves activation energy, and rate constants, but thermodynamics has to do with Gibbs, entropy, enthalpy, and heat.

Abigail_Hagen2G

The molar ratio, right?

Abigail_Hagen2G

So, it doesn't matter seconds or minutes as long as you have all the same units.

Abigail_Hagen2G

Rate constants are always positive because concentrations are always positive.

Abigail_Hagen2G

I don't think he would test us on it, but he probably wants us to have a vague idea of how to do it.

Abigail_Hagen2G

It helps determine the rate of reactions.

Abigail_Hagen2G

A first order reactions only requires one molecule of one type, where a second order reaction needs two molecules colliding.

Abigail_Hagen2G

So, that's why third order reactions are rare. It's uncommon for three molecules to collide simulataneously.

Abigail_Hagen2G

You can think of it AS 2^-X, X being each half life. So two half lives is 2^-2, or 1/4

Abigail_Hagen2G

It really depends if the solution is acidic, basic, or neutral

Abigail_Hagen2G

Redox reactions change the oxidation numbers

Abigail_Hagen2G

Yeah, it really depends if the solution is neutral, basic, or acidic.

Abigail_Hagen2G

The more positive electronic potential will be at the reduction reaction, which will be in the cathode

Abigail_Hagen2G

If you're given a diagram, the left is the anode and the right it the cathode. If you aren't given a diagram, the greater electric potential is at the cathode.

Abigail_Hagen2G

It makes sure that the flow in the cell continues.

Abigail_Hagen2G

It's all about how it makes one side of the reaction more favorable.

Abigail_Hagen2G

It was just moved from week 8 to week 9

Abigail_Hagen2G

So if it's losing energy to the surroundings, work is negative, while if the system is gaining energy, it is positive.

Abigail_Hagen2G

Yeah, you need to know the general oxidation states to see what's happening with the half reactions

Abigail_Hagen2G

It depends if it's reversible.

Abigail_Hagen2G

Yes, there are different equations to use based on if it's reversible or irreversible.

Abigail_Hagen2G

Just remember that heat and work are not state functions, most things are.

Abigail_Hagen2G

Delta U is zero because there is no potential energy because it's an ideal gas, and no kinetic energy because delta t is zero.

Abigail_Hagen2G

Since Q is K at equilibrium, when delta g is at zero, k is used.

Abigail_Hagen2G

Only the whole class is curved

Abigail_Hagen2G

Cv is for constant volume and Cp is for constant pressure, yes.

Abigail_Hagen2G

Intensive properties do not rely on the amount of substance.

Abigail_Hagen2G

This is insanely helpful, thank you!

Abigail_Hagen2G

If the equation asks for one mole its alright to put fractions in front for the coefficients.

Abigail_Hagen2G

The reversible is curved and downscoping, and the irreversible graphs are straight. It shows how less work is done for the irreversible processes.

Abigail_Hagen2G

It's an approximation for the heat capacity of a molecule.

Abigail_Hagen2G

Yeah, the problem should give you some sort of information.

Abigail_Hagen2G

It would be positive, because it requires energy to cause the phase change.

Abigail_Hagen2G

It all depends on the system and the surroundings, and what is doing work on what. Whatever is doing the work will have negative work and vise versa.

Abigail_Hagen2G

As long as there isn't any work being put in, delta u=delta h

Abigail_Hagen2G

It's just the one that states the conservation of energy.

Abigail_Hagen2G

The work is zero when there is no expansion in volume or change in pressure, because otherwise it would affect the internal energy.

Abigail_Hagen2G

The second method uses averages, so it's the least accurate.

Abigail_Hagen2G

So, can you convert between specific and molar heat capacity?

Abigail_Hagen2G

Yes, Hess's Law should be the most accurate, it doesn't rely on averages

Abigail_Hagen2G

It's sort of a baseline

Abigail_Hagen2G

Anything that isn't dependent on the path is a state function

Abigail_Hagen2G

Expanding the container would shift the reaction based on the amount of product or reactant, but with overall change, the Keq would remain unchanged.

Abigail_Hagen2G

For solving equilibrium constants, you usually just use aqueous compounds or gaseous ones

Abigail_Hagen2G

Okay, that makes more sense, thank you

Abigail_Hagen2G

The reactants have to be in excess, because Le Chatlier's Principle is based on a reaction in equilibrium, and so it's still going on.

Abigail_Hagen2G

Inert gases are relatively stable, and so they don't usually have an effect on the reaction.

Abigail_Hagen2G

It just shows how a reaction shifts to maintain stability

Abigail_Hagen2G

It affects it by making the products more favorable, using up more H2.

Abigail_Hagen2G

For homework though the one on the equation sheet should work

Abigail_Hagen2G

Is that because it's relatively stable?

Abigail_Hagen2G

It will be the same, because even if you use partial pressure instead of concentration, you would still be able to convert between the two.

Abigail_Hagen2G

They're solved exactly the same way.

Abigail_Hagen2G

K is when the reaction is at equilibrium. Q is at all other points in the reaction, and can be used to show which direction the reaction is proceeding.

Abigail_Hagen2G

Noble gases are usually unreactive, so they're unlikely to give up electrons or accept them.

Abigail_Hagen2G

Yeah, he said that we really only need to now how to calculate for strong acids.

Abigail_Hagen2G

The conjugate base is what is left after the acid gives off a proton.

Abigail_Hagen2G

So, the lewis definition is concerned with electrons while the Bronsted definition is involving protons.

Abigail_Hagen2G

Okay, that makes sense. So, when concerning bond lengths, it's the comparison between hydrogen and another atom.

Abigail_Hagen2G

Water is an example of this.

Abigail_Hagen2G

So, the number of coordination compounds depends on the number of bonds that the transition metal will make to neutralize the charge.

Abigail_Hagen2G

Yeah, we just draw the lewis structure like we always have

Abigail_Hagen2G

So water would be outside of the coordination sphere?

Abigail_Hagen2G

Okay, that makes sense

Abigail_Hagen2G

Yeah, so to tell the coordination number you have to see the number of bonds, but I think you can predict it based on the number of bonds it is able to form.

Abigail_Hagen2G

Recognizing regions of electron density does give an idea of the general shape, but the actual atoms give it a name.

Abigail_Hagen2G

Lone pairs are regions of electron density, so it does need to be taken into consideration. Like an atom with two attached atoms and no lone pairs will be linear, but if a lone pair was added, it would become bent.

Abigail_Hagen2G

Yeah, the arrow points towards the more electronegative atom

Abigail_Hagen2G

If you just had two atoms attached with two lone pairs, it would end up being bent, as the lone pairs wouldn't be able to just be opposite of each other. It would end up looking like a water molecule.

Abigail_Hagen2G

I think it depends on the atoms attached

Abigail_Hagen2G

You don't need to know the exact angle in these cases, just if it's less or more than the expected angle.

Abigail_Hagen2G

More electronegative atoms can have a negative formal charge if you need to give them one.

Abigail_Hagen2G

You really only need to do it when they ask for it. But you should when drawing resonance structures just so you can find out if it's more stable.

Abigail_Hagen2G

Just think about the number of lone electrons and the number of lines.

Abigail_Hagen2G

Yes, the central atom should have a zero charge

Abigail_Hagen2G

If the compound has no charge, then the formal charge should be zero.

Abigail_Hagen2G

Valence electrons just show how many bonds can be formed, while formal charge shows the bonds.

Abigail_Hagen2G

If there are multiple places you can place the double bond, that shows resonance. But you'll want to limit the formal charges on each atom.

Abigail_Hagen2G

Yeah, it becomes the 18-electron rule to reach a noble gas configuration

Abigail_Hagen2G

Only a few elements really need to form an octet, because after that you reach the d-orbital, the 18-electron rule becomes apparent

Abigail_Hagen2G

It's the least electronegative because it's the one that can form the most bonds

Abigail_Hagen2G

I think he said it wouldn't be on the midterm because we hadn't covered it in lecture

Abigail_Hagen2G

Okay, that makes more sense.

Abigail_Hagen2G

All you're really supposed to know for Ionization Energies is the trends for lewis structures later.

Abigail_Hagen2G

Just put the ones that are more left and more down as the central atom, as they have lower ionization energies.

Abigail_Hagen2G

Yeah, I think my TA said the same thing

Abigail_Hagen2G

Yes, electron negativity is the ability to attract paired electrons, while electron affinity is the energy used when an electron is added.

Abigail_Hagen2G

Okay, that makes more sense

Abigail_Hagen2G

n is just the energy level of the electron, the principal quantum number, and sort of shows the size of the orbital

Abigail_Hagen2G

The outer electrons feel less of an electrostatic attraction, they're shielded by the inner ones from the nucleus.

Abigail_Hagen2G

Yeah, the n-levels are just the energy levels that an electron can jump or fall to

Abigail_Hagen2G

The mass of an electron should be given, but it's 9.109* 10^-31 kg for an electron

Abigail_Hagen2G

The general unit is meters, but it wavelength can usually be put in nanometers

Abigail_Hagen2G

So, bigger objects have a wavelength way smaller than 10^-15, so they're not detectable according to de Broglie's equation.

Abigail_Hagen2G

So, when we use the equation, we end by doing Ef-Ei?

Abigail_Hagen2G

Okay, that makes sense. So, de Broglie's equation shows the relationship of the wavelength, mass, and velocity of a small particle, and Rydberg predicts the energy of an electron moving between energy levels, but only for hydrogen.

Abigail_Hagen2G

When it says measurable wavelike properties, it just means that it's not smaller than 10^-15, because that's not detectable.

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