CHEMISTRY COMMUNITY

David Jen 1J

Many questions will straight up tell you which step is the slow step, but in case it doesn't, the slow step tends to make up the overall rate law.

David Jen 1J

n in this case isn't moles of a gas but number of electrons transferred.

David Jen 1J

When do you use Delta S=qrev/T and when do you use Delta S = nR lnv2/v1

David Jen 1J

When do you use this equation? Is it for only irreversible volume expansions? Are there any limitations to the usage of this equation?

David Jen 1J

For a experimentally derived rate law, is it possible to have more than one specific pathway that would lead to the rate law?

David Jen 1J

It is definitely possible but I think the odds are very slim.

David Jen 1J

Unless the question gives you all the variables needed to calculate the rate law, probably.

David Jen 1J

# order is the summation of each individual reactants order. Thus assuming that one of the two reactants second order and the other is first order, it would be a third order reaction.

David Jen 1J

I'm assuming half reactions will probably not be given on the exam because it's fundamental to understanding how to balance redox equations. But I'm not sure.

David Jen 1J

By saturation, he means that all the enzymes are currently in use and even by adding more of the reactant, the reaction rate wouldn't increase.

David Jen 1J

Order of a reaction is the number of molecules/elements that need to come together at an instantaneous moment to allow the reaction to proceed. As a result, higher order reactions are more rare.

David Jen 1J

The way I remember it is that the Anode is the place electrons flow Away from.

David Jen 1J

Yes, you should almost always include states of matter unless the question tells you that you don't need to.

David Jen 1J

I tend to compare it to the original, unbalanced equation that the problem gave me. Odds are, the phases will be identical after you balance it. Then, for H2O it would be liquid, and ions would be aq.

David Jen 1J

I think you multiplied stoichiometric coefficents to the standard potential. Standard potential doesn't change with the stoichiometric coefficients. Hopefully this will solve your problem.

David Jen 1J

Could someone explain to me how shorthand notation works?

David Jen 1J

Qrev is the heat transferred from a reversible process.

David Jen 1J

Cell potential is a path function because we cannot subtract final cell potential from initial.

David Jen 1J

Work done to the system is negative and work done on the system is positive.

David Jen 1J

You would have to ask a TA during their office hour.

David Jen 1J

Why do we power W with avogadros constant? Is it because we are calculating the delta S in units of mol?

David Jen 1J

As long as you pay attention to what the question is asking, there should be no problem.

David Jen 1J

Another question, why is it that the greater the Svap, the more ordered it is?

David Jen 1J

K=1 is rare because it means both sides of a reaction isn't really favored, meaning that the reaction won't go in any way specifically.

David Jen 1J

Yes you can as long as your units match in the end.

David Jen 1J

How do you calculate Svap?

David Jen 1J

I think work done by the system is negative and work done to the system is positive.

David Jen 1J

It happens to me too! I think the best way to lessen careless mistakes is to double check as you do a problem. I've found that that has worked for me.

David Jen 1J

Work is energy transferred from one thing to another.

David Jen 1J

I'm probably going to take chem 14c and BL together next fall.

David Jen 1J

In a closed system, matter cannot be exchanged, thus volume won't change as well

David Jen 1J

We would be focusing on change in heat rather than temperature although they technically go hand in hand.

David Jen 1J

It means we are assuming that no energy is lost from a reaction and stays within the system.

David Jen 1J

Kelvin is equal to Celsius plus 273, thus if you're adding one to Celsius, you are also adding one to kelvin.

David Jen 1J

You can switch it, but when u switch it, make sure to switch the sign of enthalpy too.

David Jen 1J

That's correct!

David Jen 1J

is there a specific cut off point for this though? Like a difference of 10^-3 or more?

David Jen 1J

Phase change is when a substance changes from one state of matter to another

David Jen 1J

if its a reactant, -x, if its a product, +x

David Jen 1J

It probably depends on the concentration of vapor hitting your skin at once.

David Jen 1J

For anyone wondering, midterm is this Friday.

David Jen 1J

a high kb also indicates a strong base and a low ka would also indicate a strong base.

David Jen 1J

Only count moles of gas.

David Jen 1J

I think it highlights the reversible action of a acid base reaction. In cases where the acid/base aren't strong, the conjugates could potentially play a role in regulating environments (pH), such as bicarbonate in the ocean and our blood.

David Jen 1J

use kelvin.

David Jen 1J

The good thing is, there is essentially no homework graded for this class except sapling, and you have infinite attempts per question, so I wouldn't worry about sig figs in that aspect.

David Jen 1J

Yes, Ka is for acids and Kb is for bases.

David Jen 1J

We include gases, except for inert gases.

David Jen 1J

Q calculates the same way as K, but Q calculates at concentrations that aren't equilibrium.

David Jen 1J

I heard of step up sessions but I don't know what happens there. Could someone fill me in on those? I'm kind of interested in attending one this quarter.

David Jen 1J

It can feel a bit overwhelming, something that has helped me was the active topic section you can find under quick links, it gave me a way to find relevant topics that I can reply to!

David Jen 1J

An inert gas is a element that doesn't react to other elements because it's valence shell is filled. Often it is the noble gases because the valence shell is filled.

David Jen 1J

Only gases are counted!

David Jen 1J

How would you be able to calculate K if you're only given concentrations for Q? They would typically give K to you right?

David Jen 1J

If a molecule has the prefix bis, tris, tetrakis, etc, would that prefix be counted when looking to name the coordination compound? I'm asking because, for question 9c.3, part d named the compound: sodium bisoxalato(diaqua)ferrate(III), when if following the rules, aqua would be first instead of oxa...

David Jen 1J

Me too. Also, does Al3+ make it's surrounding solution acidic because it can give off protons or is it accepting electrons?

David Jen 1J

Can trans- orientated ligands be bidentate? More specifically, C2C04?

David Jen 1J

If the pH is low enough, can a strong acid become a conjugate base?

David Jen 1J

When learning about Amphoteric molecules, I noticed that the strong acid H2S04, when deprotonated, has a similar structure as other Amphoteric molecules. However, can it be considered a amphoteric molecule if it is a strong acid?

David Jen 1J

So is dentate synonymous with ligand?

David Jen 1J

(en) is short for ethylenediamine. I'm pretty sure there are more compounds that have similar naming nature so make sure to read about those ones too as it might be on the test!

David Jen 1J

Hemoglobin is 4 myoglobin put together. As a result, hemoglobin can carry more oxygen at one time.

David Jen 1J

I think amphoteric compounds tend to typically have polar bond when containing a H. As a result, there is a H to be donated. If it is donated, there is potential for it to re-accept the H as well.

David Jen 1J

Lewis bases donate electrons, Bronstead bases accept protons. Essentially they are the same thing.

David Jen 1J

I am currently waitlisted for the winter quarter and according to Prof. Lavelle, I'll be able to get in. But I'm wondering how PTE and enrollment works. Could someone explain it? Thanks.

David Jen 1J

Hydrogen is also an exception to the octet rule!

David Jen 1J

Dipole moments can only be cancelled out on a Tetrahedral Atom when it is four of the same elements bonded to a central element. (CCl4)

David Jen 1J

It has to do with dipole moments. A molecule could have all polar covalent bonds and still be nonpolar due to it's shape because the bonds are directly 180 degrees away from each other. H20, because it is bent, not linear, has dipoles that aren't cancelled out. BeCl2, on the other hand, also has pol...

David Jen 1J

I also was very confused with this problem, is there any way it has to do with the number of double bonds as well?

David Jen 1J

I'm pretty sure we need to memorize all the ones Prof. Lavelle goes over.

David Jen 1J

To determine covalent character in ionic bonds, you find the DEN of the elements. The lower the DEN, the more covalent it is.

David Jen 1J

Out of curiosity, does anyone know if there is a certain max number of electrons in a expanded octet?

David Jen 1J

Yes. It is super weak and only lasts for a brief moment.

David Jen 1J

Hi. Electron density is basically where a certain electron could be at any given point.

David Jen 1J

Prof. Lavelle said in his class website that midterm 2 is up to chemical bonds, does that mean vsper model are not part of the midterm? And if anyone knows, where in the textbook does content go up to? Thanks.

David Jen 1J

And if so, does overall formal charge sum also always indicate the overall charge of the molecule?

David Jen 1J

Just to clarify, resonance structures are most stable/tend to favor positions where formal charge on each atom is zero right?

David Jen 1J

In this equation, the lone stands for all of the free/unbonded electrons. Don't think of it as lone pairs as you might count two electrons as one pair and plug 1 in the equation. Think of it as the individual electrons, so in this example it would be 2 electrons and you would use 2 in the FC equati...

David Jen 1J

Is there a way to predict which element in an atom will have the radical? this came up in textbook problem 2C.5. The radical went with Cl rather than O, and I can't explain why except for that Cl has an odd number of valence electrons to start with. Hi! I believe that the placement of the lone elec...

David Jen 1J

To calculate electronegativity, there is a specific periodic table that shows the electronegativity of every element. However, I think when not asked to detemine the specific DEN, one can base it off of periodic trends (ie far left is more electromotive than far right) and determine an idea of elect...

David Jen 1J

In the formal charge formula, F= V- (Lone - Bonds/2), does lone stand for lone pairs and unbonded electrons or just lone pairs.

David Jen 1J

Lone pair electrons are pairs that have not been bonded and naturally belong to said atom.

David Jen 1J

The octet rule is the concept that every atom wants to fill it's valence shells to achieve stability and lots of atoms do it by filling their shells, which can contain up to 8, with some special exceptions. As a result, the octet rule is a baseline for creating the structure of compounds by trying t...

David Jen 1J

Lewis base is just something that donates electrons. I wouldn't necessarily say all negative charges mean it's a lewis base but it's a good way to start off if asked to find a lewis base.

David Jen 1J

Polarity means that there is an unequal charge, an unequal distribution of a shared electron. Thus a polar covalent bond has polarity because of an unequally shared electron.

David Jen 1J

The grades are out!

David Jen 1J

5 d orbitals means that there are 5 orbitals in the d orbital. Each orbital holds 2 electrons.

David Jen 1J

This is because the lower the molecule on a table, the bigger it is, thus it is easier to remove an electron from it's outer shell compared to a smaller molecule because the level of attraction is lower.

David Jen 1J

Avogadro's number represents the number of atoms in one mole. Thus, we should use it whenever a question asks for something regarding atoms.

David Jen 1J

The particle model is supported by atomic spectroscopy.

David Jen 1J

So we don't need to study 1.D?

David Jen 1J

I like to do practice problems and read the textbook. Practice problems is where I mostly retain information from.

David Jen 1J

Does anyone know if there will be Schrodinger related questions on MT1?

David Jen 1J

Hi, mmol is a millimol, which is 1/1000th of a mol.

David Jen 1J

For general problems, it is round up. But remember that when dealing with mols in empirical formula problems, we multiply to the nearest whole number.

David Jen 1J

I like to use whatever is on the formula sheet to like 4 decimals.

David Jen 1J

Hey Chesca, electrons don't technically jump/skip levels, they just have enough energy to go all the way to N=4. That means they'd have to have enough energy to make it through n=2 and n=3 before it could make it to n=4

David Jen 1J

I'm also a bit confused on this topic. Do we just take the difference between n-levels? For example, if an electron starts at the n=6 level and falls to the n=1 level, did it "pass" 5 spectral lines? And if an electron starts at the n=4 level and drops to the n=2 level, did it "pass&...

David Jen 1J

During Friday's lecture, Dr. Lavelle shows us the experiment where they shine light through an area with openings and light enters and appears where there isn't an opening. If the light was not a wave, the light would just shine straight instead of bending. Because the light was refracted, we are ab...

David Jen 1J

I searched it up and yes light does lose energy the further it travels. But for it to lose energy, it would have to travel super far. That's why we can see stars but aren't super bright.

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