CHEMISTRY COMMUNITY

Caroline Zepecki

The catalyst lowers the activation energy, making it easier for both the forward and reverse reactions to occur, thus speeding them both up.

Caroline Zepecki

We should either be given the graph to figure it out or given the information for an experiment.

Caroline Zepecki

It's correct whether in fraction or whole number form, because the equations we use relate the two in ratio form anyways.

Caroline Zepecki

Zero order reactions depend only on K, because [A]^0 =1, so it doesn't effect the rate.

Caroline Zepecki

For a second order reaction, it would be linear.

Caroline Zepecki

Over a very very long period of time graphite will turn to diamond, but graphite is in its more stable energy form. It has a super high activation energy/energy barrier though

Caroline Zepecki

When something has a lower delta G, it's in a lower energy form, and thus less likely to react. If it's prone to stay in the lowest energy form, or in reactants, you can tell that it's thermodynamically stable

Caroline Zepecki

Make sure to look at your notes for the first rate, second rate, and zero rate reactions. They're all pretty similar but it's important to know where they come from, especially when looking at the half life equations.

Caroline Zepecki

Means that it's stable enough to stay in reactant form- basically has a high energy barrier but still a negative G value.

Caroline Zepecki

Instantaneous rate breaks up into infinite intervals, whereas average relies only on the data points you're given so it's far less accurate.

Caroline Zepecki

"dissolving" in essence is losing electrons. Thus, as oxidation happens as part of the half reaction on metals, electrons are being lost and the metal is dissolving away

Caroline Zepecki

Means graphite form of carbon, helpful to know that this is one of the more stable forms

Caroline Zepecki

Caroline Zepecki

Salt bridge allows for ion transfer when anode and cathode are completely isolated from each other

Caroline Zepecki

if there are no solids in the reactants, but are in the products, can consider a precipitation reaction.

Caroline Zepecki

It is the charge of 6.02 x 10^23 electrons

Caroline Zepecki

we only know the oxidation number for certain specific elements, but you can determine the oxidation numbers you know for the other elements using the ones you know combined with the final charge

Caroline Zepecki

The elections gained by iron in the process, or the reduction, is the forming of the rust in the reaction

Caroline Zepecki

Voltage is the amount of energy to the electric charge, and one volt is equal to one joule of energy for each coulomb of charge

Caroline Zepecki

The half reactions are the individual Reduction and Oxidation reactions of a Redox reaction

Caroline Zepecki

How would you go about calculating energy density?

Caroline Zepecki

Microstates refers to the possible arrangements, so for example, when calculating W, it would be micro states ^ # of atoms

Caroline Zepecki

For a reversible equation, total entropy would be equal to zero. For something like combustion, that is irreversible, you would have a significant change in entropy

Caroline Zepecki

You can only use the ∆G°=-RTlnK equation when the system in question is at equilibrium, otherwise you have to use the other equations.

Caroline Zepecki

If a water bottle is vacuum sealed, then technically heat is not escaping so no energy is being exchanged with the surrounding environment

Caroline Zepecki

Technically, it applies to all systems because energy is never lost its just transferred to "the universe", or the greater system that every isolated system is technically part of.

Caroline Zepecki

yes, because the number of different positions are directly correlated to the W value, which then effects entropy.

Caroline Zepecki

More particles -> higher degeneracy -> more entropy

Caroline Zepecki

If the temperature is constant, but you have changing pressure instead, you would use S = nKln(p1/p2), so same equation but replace V2 with P1 and vice versa because they're inversely proportional.

Caroline Zepecki

When calculating Gibbs free energy, do you use the same method as you would for Hess's law?

Caroline Zepecki

all we need to know for know is just that delta U = q + w, because we haven't looked at what happens when pressure starts changing

Caroline Zepecki

Can someone explain Hess's law and when we would need to use it?

Caroline Zepecki

what is the difference between extensive and intensive properties? just that they are affected by volumes?

Caroline Zepecki

Can you assume that inert gasses wouldn't affect enthalpy calculations then?

Caroline Zepecki

Enthalpy is specifically the energy absorbed/released, so its only going to be equal to internal energy at a constant pressure and volume.

Caroline Zepecki

If there are any aq you have to use concentrations: it's possible to convert from PP to concentration but not vice versa.

Caroline Zepecki

you only include gasses and aq things in the chemical equilibrium equation. That being said, water as a gas is included.

Caroline Zepecki

if you know the pka, you can use the equation PkW = PkA x PkB.

Caroline Zepecki

Kp is for partial pressures of gasses, Kc on the other hand is the equilibrium constants

Caroline Zepecki

in an exothermic reaction, increasing heat shifts towards reactants. in endothermic reaction, head shifts towards products.

Caroline Zepecki

Smaller K value -> more thermodynamically stable

Caroline Zepecki

Left shift means that the reaction is going from right to left, thus forming more reactants. The opposite is true with products. Just look at the written equation and whatever is left or right of the arrow is the direction of movement and what's being formed

Caroline Zepecki

You most likely should be given the partial pressure to complete a problem where you're either solving for Qp or Kp.

Caroline Zepecki

The reaction quotient is unitless because the units cancel out.

Caroline Zepecki

For calculating either Q or K, every time you online include gasses or aq. Never solids or solvents in the calculations

Caroline Zepecki

how does Kc take into account the values of partial pressure?

Caroline Zepecki

Q is the constant of concentration at any point during the reaction, whereas K is the constant of concentration at equilibrium.

Caroline Zepecki

would any compound solids and liquids just be considered spectators in the reaction as well?

Caroline Zepecki

Is the Gibbs free energy constant the same for Q and K? or can you only use it with the K value?

Caroline Zepecki

How do you determine which gasses can be considered "ideal"?

Caroline Zepecki

When determining the coordination number, and/or the number of binding sites, you look at the number of ATOMS with electron pairs, not the number of electron pairs. Hope this helps.

Caroline Zepecki

I'd recommend just focusing on memorizing the chart Lavelle emailed, but as you do more practice too you will begin to pick up on the main ligands and their charges.

Caroline Zepecki

Pretty much the number of bonds that the coordination compounds has formed is the coordination number.

Caroline Zepecki

How are you supposed to determine whether a compound is mono, bi, tri, or polydentate? I know you're supposed to look at bonding sites, but does each lone pair of electrons count towards the coordination number?

Caroline Zepecki

You determine roman numeral by finding the oxidation number of the metal. You determine the charge on the ligand, and if the coordination compound is an ion, then you can find the oxidation number by determining what number will make all charges true.

Caroline Zepecki

does the oxidation number come at the end of the entire compound? or just the transition metal

Caroline Zepecki

When you do equations with the equilibrium constant K though, its important to note that although the equation is products/ reactants, water will be equal to zero.

Caroline Zepecki

The pH scale definitely can not go negative because it is the factor 10 of H+ ions, so from a mathematical standpoint it would make no sense to have a negative concentration of H+ ions.

Caroline Zepecki

Technically no because it's so rare that noble gasses even engage with anything that they're considered inactive. The definition of a base is that it receives electrons.

Caroline Zepecki

In some solvents, the acid, although weak, will dissociate more.

Caroline Zepecki

Anions create a static field that help to break down electron orbitals, mainly d and f by the crystal field theory

Caroline Zepecki

are the metals always named last then even if they're names are later in the alphabet?

Caroline Zepecki

A coordination compound is a metallic central atom surrounded by other atoms or molecules that are known as ligands or complexing agents.

Caroline Zepecki

if you have a coordination site and a bond inside on of those compounds, does that mean that the coordination number would be four then?

Caroline Zepecki

if you only use ate for a negative charge, what do you use for positive and neutral charges?

Caroline Zepecki

The strongest is dipole dipole followed by ion-dipole.

Caroline Zepecki

Oxygen can have single, double, or triple bonds depending on the molecule and corresponding Lewis structure.

Caroline Zepecki

Neon gas yes, is part of the normal electronegativity trends. Noble gasses, on the other hand, don't follow the pattern because they all already have filled valence shells.

Caroline Zepecki

Does distortion in regards to polarizability necessarily mean the ability to form octets? or just the ability to attract electrons from another atom's electron cloud

Caroline Zepecki

What is the relevance of having a sigma vs. a pi bond? is there an effect on bond strength and energy?

Caroline Zepecki

We know that double bonds are shorter ands stronger than single bonds, and that triple bonds are even more so than double. But how do the length and strengths of these bonds effect the different energies?

Caroline Zepecki

Is it possible to have a resonance structure where the bond that changes with each different possible structure is a triple bond instead of a double bond??

Caroline Zepecki

Do the functions of these particular ligands effect the structures of the molecules? Or just the composition?

Caroline Zepecki

Magnetic quantum numbers can range from -l to l, and there are either going to be 1, 3, 5, 7 depending on the value of l

Caroline Zepecki

Are there specific molecules that we need to memorize the VSEPR models for then or will they be given?

Caroline Zepecki

Are there only particular atoms/molecules that allow for expanded octets? Also is there a way to explain why this is possible for some and not all?

Caroline Zepecki

What is the pattern on the periodic table that we're supposed to memorize for determining electronegativity?

Caroline Zepecki

That being said, you can look for patterns because the further two elements are from each other on the periodic table they'll have greater dipole moments.

Caroline Zepecki

Because the values are only going to be +1/2 or -1/2, I feel like just doing a + or - will be sufficient to distinguish.

Caroline Zepecki

Technically, if the question asks if the wavelength is detectable, or more often it will ask if there are "detectable wavelike properties" that means that it wants to know whether the wavelength is greater than 10e-15 or not.

Caroline Zepecki

It's important that you memorize the different groups while looking at the periodic table. The lefthand side has the s groups, the middle the d groups, and the right side the p groups. Then, the constant that determines which orbital it is corresponds to the period # (for s and p groups) and period ...

Caroline Zepecki

As you move down the period, it would decrease because the repulsion amongst the electron cloud decreases, which lowers the ionization energy.

Caroline Zepecki

Do uncertainty values always have to be whole integers? also when giving the "total uncertainty" do you always know to just add the numbers or will it ever specify for the range?

Caroline Zepecki

As seen through the Aufbau Principle, it's imperative to fill the 3d energy level before you can fill the 4d.

Caroline Zepecki

Yes, there are always going to be n-1 possible values. But 0 is included in those, so it would only go from 0-5!

Caroline Zepecki

Yes, there are always going to be n-1 possible values. But 0 is included in those, so it would only go from 0-5!

Caroline Zepecki

I think it just means to use the De Broglie equation because the De Broglie equation is derived from the equations E=pc, c= wavelength*frequency, and E=hv which we have learned before. However, this equation only works for any particle with a rest mass, momentum, and wavelength so if it asks for th...

Caroline Zepecki

Are there specific values somewhere on the periodic table that can be used to determine atomic radius or do you just have to determine comparatively by location?

Caroline Zepecki

If the energy isn't enough to pass the threshold, the photon won't be able to remove electrons. The energy of the photon needs to be greater than the energy of the electron to remove it.

Caroline Zepecki

In class, Dr. Lavelle mentioned that we only really need to be concerned with three of the types of orbitals. Those that correspond with the left of the periodic table, the first row through the middle, and the righthand columns respectively. Is this the case? Also how do we determine which orbitals...

Caroline Zepecki

The extent to which black bodies were discussed in the textbook was pretty much a general definition. So likely we just have to know that its a concept in quantum mechanics that there's a substance of some sort that absorbs all types of radiation and waves of light.

Caroline Zepecki

Technically, the movement of any matter (such as the water in a bucket example someone mentioned above), is wave movement. BUT, if you break anything down to an atomic level, wouldn't it have particle movement instead? But then, does all matter definitely have wave movement instead or is that imposs...

Caroline Zepecki

When looking at energy levels, is there a direct correspondence of 1 photon -> 1 energy level? wouldn't it depend on the intensity of a photon, or is the intensity the same for all photons, and thus a constant relationship between photons and energy level?

Caroline Zepecki

how does the radius of atoms change as electrons become excited/energy levels shift? is there a linear increase/decrease in radius?

Caroline Zepecki

When is an example of when you would use the Rydberg equation?

Caroline Zepecki

I'm trying to visualize some of what we went over in lecture about how shorter, less intense wavelengths have enough energy in a single photon to displace elections. I was wondering what about photons changed with wavelength (is it intensity?), and if there's an equation that relates them?

Caroline Zepecki

If it's a problem that requires you to use molar masses, it would make sense that you definitely take them into account. For example, if in a word problem you're given masses to the ten thousandths place, and you find molar masses only to the thousandths place, you would need to round the given mass...

Caroline Zepecki

Technically, it's impossible to have two limiting reactants, because that would mean that both of the reagents would be being used in full. And the definition of a limiting reactant is the one left over in excess. Thus, you could really only have one or zero limiting reactants because you can have a...

Caroline Zepecki

It has been a few years since I've been in chemistry, and I was hoping to clarify some of the basic sig fig rules. Is it customary to round to the hundredths or the thousands place when presenting a mass value (g) as your answer? Also, do the rules for this vary greatly based off of what type of pro...

Caroline Zepecki

It's important to know Avogadro's number because it's equivalent to the number of atoms in a single carbon 12, and normalized as a way to measure a single mole. Whenever we need Avogadro's number, I think it will be given to us, but most regularly you'll need to use it in order to convert from moles...

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