CHEMISTRY COMMUNITY

Javier Perez M 1H

Definitely using a chart is helpful because not all of these have oh or h in their name making it harder to identify the type of substance.

Javier Perez M 1H

The more space for particles to move the higher the entropy. The lower the atm the bigger the volume.

Javier Perez M 1H

In a sense, it's like looking at exothermal and endothermal graphs where we only focus on the initial and final states.

Javier Perez M 1H

yes K is typically a ratio but sometimes pressures can be added to an equation in a similar manner where the pressures are to the power of thier coefficient and where the whole fraction is not equal to 1.

Javier Perez M 1H

treat T as x and remember that the given temperature becomes into a number which you will divide by the constant attached to T to get your T final. Of course, using numbers on both sides. Usually, double changes in the state of one quantity tend to just be added like the ice fusion value on one of t...

Javier Perez M 1H

Definitely, things on both sides are to be canceled.
However, how do we add the energy values and how do the coefficient ratios relate to them?

Javier Perez M 1H

Definitely keep in mind the units. Atm seems to be the most common.

Javier Perez M 1H

The main thing with closed systems is that you can't add anything into the inside of the system besides things like heat that can go through the walls.

Javier Perez M 1H

Well, when it comes to an enclosed gas such as in a valve, by pushing air into it im inputting work into the system possibly introducing more pressure, or when you compress a gas in general that is positive work as it is going into the system. However, when the gas pushes back that is usually consid...

Javier Perez M 1H

Textbook problems help sometimes. Im gonna try attending Lavelle's office hours hopefully that helps a lot.

Javier Perez M 1H

Remember that in reverse, so do your moles of products and reactants flip.

Javier Perez M 1H

It most likely has to do with concentration staying constant, that is the original gases.

Javier Perez M 1H

if pressure doubles volume halfes. Therefore, molarity and pressure are quite related.

Javier Perez M 1H

yeah Pkw is basically the total possible Ph or ph of 14 which is usually Pha x Phb.

Javier Perez M 1H

It was more difficult compared to 14A midterms. The questions weren't like what I prepared for. Would have loved to have prepped with quite similar formats.

Javier Perez M 1H

It depends on what is given. Think of it as an equilibrium reaction where if the products are given instead of reactants you have to decrease products to get your reactants and then use reactants to possibly find the eq concentration of your product.
right everyone? or am I wrong?

Javier Perez M 1H

Definitely, use the delta H to determine whether is endothermic or exothermic.

Javier Perez M 1H

Definitely, as stated above do not include nongases nor solvents such as the common H2O except when itls part of the reaction not acting as main solvent that you include the concentration of H20.

Javier Perez M 1H

-log(x) function is used to find both the Ph and Poh given the concentrations of OH- or H+. These concentrations are plugged in as x. However, if you are solving and have a Ka value then you cannot directly determine the Poh, you must calculate Ph then -14 and you'll get your Poh.

Javier Perez M 1H

If the Ka or Kb is < 10^-4 then it is fine to ignore the -x from the initial mols.

Javier Perez M 1H

How are we to determine if a chemical equation is endothermic or exothermic? Will it be provided or can we determine this from K values?

Javier Perez M 1H

Another factor that might help is whether the pH is higher or lower than 1 or 14.

Javier Perez M 1H

Yes the process for solving for partial pressures is quite the same as calculating concentrations. However be aware that you might get cubed equations and there is a different process for solving them.

Javier Perez M 1H

In terms of test taking, I recommend using the ICE box now in order to become more efficient and avoid errors during exams.

Javier Perez M 1H

Yeah this is a bit confusing given that he had mentioned that the concentration had to be smaller than 10^-3 but most recently 10^-4. Lavelle please clarify this.

Javier Perez M 1H

So when using PV=NRT temperature is supposed to be inputted in Kelvin? How come though fro most of the questions so far we are being given temperature in Celcius?

Javier Perez M 1H

The question is most likely to ask for one while giving you the units of the other. That is when you rely on PV=NRT to get the units you need based on what you are being asked for.

Javier Perez M 1H

Where do we usually encounter the bar unit?

Javier Perez M 1H

Since a quadratic equation has two answers one being negative and the other being positive, you will be going with the positive answer given that there is no such thing as negative matter. However, what if we get two positive answers?

Javier Perez M 1H

Where can we find all the answers to the textbook practice problems? I believe it might be on Lavelle's website but I cannot recall under what tab. Given that this concept requires all sorts of equation solving back and forth it might be a good idea to gain a better grasp by literally applying it in...

Javier Perez M 1H

Good question, it has to do with the components of your acidic molecule. Generally when no O is present just H and some P orbital atom the most electronegative and biggest, towards the bottom makes it more acidic. The more Os are present the more acidic. The higher the overall charge the more acidic...

Javier Perez M 1H

bis, tris, etc is generally used to name molecules or atoms with more than one bond. It seems the mono-, di- prefixes (which indicates how many atoms or molecules are present) is canceled out when dealing with these complex bonds.

Javier Perez M 1H

That is true, bond length relies on center to center distance. However, bonds also decrease these lengths theoretically when bonding more than once.

Javier Perez M 1H

Definitely, this exam had very little time for the amount and type of questions. Many students either didn't finish or rushed through half of it. Both the mathematical questions and the content questions do rely on more thinking than a usual simpler question on the midterms. Being a bad test taker t...

Javier Perez M 1H

How do we solve for these and what is the relationship among them?ph, poh, Ka, Pka
Also when is it that we need molarity in these calculations?

Javier Perez M 1H

Hi, how do I know when an acid is strong or weak? Similarly, how do I know the stability such as leaning more to the right or left, etc?

Javier Perez M 1H

Resonance structures tend to be stable when there aren't that many charges around it, the shape is in a way balanced, and the pull of bonding atoms canceling out.

Javier Perez M 1H

Definitely memorize the list that Dr.Lavelle gave during the lectures it will assist you. Also probably try to see how OH molecules are formed as that will reveal as well which one is stronger and weaker.

Javier Perez M 1H

Most definitely, one bond is a sigma everything after in that same bond region would be Pi bonds because those are the ones that stop rotation for the most part.

Javier Perez M 1H

Strong acids have weaker bonds meaning the larger the space in between two atoms the stronger it is.

Javier Perez M 1H

Why is oxidation state important in acids?

Javier Perez M 1H

Will our TA actually go over with us the previous midterms we did if we schedule the appointment? My TA had mentioned something about not being able to view them or something.

Javier Perez M 1H

Nonpolar bonds are bonds between atoms of the same element as there is no difference in electronegativity and they share the same number of electrons(not sure if electronegativity is a requirement though). A nonpolar molecule is a molecule that has balance forces all around it. For example, a centra...

Javier Perez M 1H

I would recommend that you see molecules in multiple planes of 360, there fore you just divide the 360 degrees by the number of bonds to get the average bond angle in between atoms in that plane, and if there are lone pairs in that plane it would be safe the assume that the angle would be less.

Javier Perez M 1H

Dipole moments only occur when dipoles cancel out or when the forces are said to be balanced. The best way to determine if the forces are balanced around the central atom is to determine the shape and determine all forces around that central atom in the molecule.

Javier Perez M 1H

Two or more lone pairs means you have a bent structure. Usually, you can tell polarity by looking at the molecule's shape. If it looks uneven it is most likely to be polar.

Javier Perez M 1H

Electronegativity is Electron Affinity (energy released from gain of electrons) plus Ionization energy (Energy needed to release an electron). Thus, all three are basically highest in your top right of your periodic table and decrease as you go left or down.

Javier Perez M 1H

Definitely, it will cover all the term's material. However, as long as you been studying well for the last two exams the final should just be a small addition of the new content.

Javier Perez M 1H

Yes, your solid bonds or triangle-looking bonds are those facing you, while the dashed triangle ones are those facing away, and while the solid lines or regular bonds are those bonds parallel to you.

Javier Perez M 1H

Hydrogen is just one of the very few elements that will never be your central atom. Every other element can be a central atom for the most part as long as they are the one with the least electronegativity in the molecule.

Javier Perez M 1H

Whether an element is polar or not might have to do with whether the element is in ion form or not and the overall properties of the element. There are elements that are very reactive.

Javier Perez M 1H

Definitely, if the vectors don't cancel out the atom will be polar. However, are ions always polar since they have a charge?

Javier Perez M 1H

How do molecules form resonance structures? I know that at times it's a molecule that puts in both electrons for a bond to form but what are the main rules?

Javier Perez M 1H

Why is it that a very electronegative atom with an atom with a bigger atomic radius is harder to dissolve than the same atom but with another atom with a smaller radius?

Javier Perez M 1H

When it comes to drawing Lewis structures, is our central atom such o in H2O always nuetral or when is it that it gains a positive or negative charge? How am I supposed to know?
In ions can outer atoms hold a positive charge or only negative?

Javier Perez M 1H

I think reading the textbook is sometimes more of a supplement when not understanding things, however it better to read it to better grasp the concepts or engrave them into your memory.

Javier Perez M 1H

It depends wether its octet is satisfied already. It also depends on its chemical,atomic affinity.

Javier Perez M 1H

electron-negativity does have an impact on bond lenqth. The stronger the smaller the bond length. Simply look at it as a sphere the bigger the sphere or the atom in size due to electron cloud being pulled less by the nucleus due to the amount of electrons and nucleus pull.

Javier Perez M 1H

Each letter shell has a different amount of orbitals and so forth. p=3 d=5 f=7

Javier Perez M 1H

More electrons = larger radius
However, there is a bigger increment once they start going into other orbitals or passing N=2.

Javier Perez M 1H

By what day do we have to post every week?

Javier Perez M 1H

He is probably going to post them in a week, I believe they may be curved or something so that might be why he is going to take longer.

Javier Perez M 1H

Most definitely, when you don't understand something its good to consult the textbook. If that doesn't work ask TAs and UAs. If you can't reach them then just look it up in the internet there could be articles or videos on the topic.

Javier Perez M 1H

Hi, can someone explain to me what the significance is of each and how to find the number of electrons when Ml is given? Im having trouble understanding what ml means the most when finding the number of electrons.

Javier Perez M 1H

As for what kind of concept questions there will be, off the top off my head I'd say definitely know the wave model, diffraction, the photoelectric effect, the particle model, Bohr frequency condition, atomic and molecular spectra, conservation of mass, and conservation of energy. The study guide a...

Javier Perez M 1H

Will we be provided with conversion units for the exam? (such as how many nanometers are in a meter and ml in a liter)
Or are we expected to memorize this?

Javier Perez M 1H

Will how to solve for wave functions be on the exam?
Schrodinger's equation

Javier Perez M 1H

As of now the error has not been fixed in terms of the randomization. It also seems there are no randomizer options from our end.

Javier Perez M 1H

That is exactly the same question I had because of sapling homework questions 6 and 8 I believe where in the Rydberg equation n1 and n2 are swapped. Can someone please verify that these flip accordingly wether its an emission of absorption.

Javier Perez M 1H

What is intensity and what is frequency?
As far as I know frequency is just the amount of cycles per an amount of time or waves. However, what exactly is intensity?

Javier Perez M 1H

If you go the route of buying a webcam I would recommend Fry's or Amazon. Possibly B&H as well. Hope this opens your options.

Javier Perez M 1H

Definitely doing a lot of practice problems helps. However, what is the best way to take notes during the recorded lectures? Sometimes I wait for him to go through the whole slide and other times I take the notes as he speaks and thing pop up on the slide.

Javier Perez M 1H

Yes, if your question has 4 significant figures then your answer should have 4 significant figures.

Javier Perez M 1H

For the exam, my TA said that you will need some sort of camera showing your workspace. If your desktop/laptop doesn't have a camera then you will be forced to take out your phone and login to the zoom session via phone where through that camera they will monitor you during the exam.

Javier Perez M 1H

Well for this question you will have to keep in mind the following two equations E(photon energy)=hv and c=wavelength*frequency. You are only given K.E and Frequency. You basically plug in frequency into your "C" equation to get the wavelength then plug in your wavelength into your E(photo...

Javier Perez M 1H

Hope this helps when it comes to significant figures: non-0 numbers are considered significant figures numbers including zeros in between non zero numbers ae considered significant figures as well Zeros in front, or "leading zeroes" are not counted as significant numbers Zeros in back, or ...

Javier Perez M 1H

Will we be expected to know how to read or draw compound drawings/ structures for our exams? (like question 10 on sapling)

Javier Perez M 1H

Also where can we learn to read such symbols or way of displaying a chemical reaction without the lettering we usually use?

Javier Perez M 1H

Was this chemical reaction balanced already or did we have to balance it? The one provided in the question

Javier Perez M 1H

The trial I believe is a week long (7days to be exact) unless they are providing us with an extended version.

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