CHEMISTRY COMMUNITY

Gigi Elizarraras 2C

Because the first step is fast there will be a build up of products that eventually o back to being reactants in a reversible chem equation. The process will be assumed to be at equilibrium in the forward and reverse processes:)

hope this helps!

Gigi Elizarraras 2C

A catalyst will not appear in the overall reactions as it is not really apart of the process, but it an additive just meant to increase the rate:)

hope this helps!

Gigi Elizarraras 2C

Catalysts usually show up in the reactants of the first step, and intermediates are usually produced in the first step:) as well as intermediates become later reactants

hope this helps:)

Gigi Elizarraras 2C

The pre-equilibrium approach is used wen we want to get rid of an intermediate as they are not included in the rate law:) if the first step was the slow then we would not need to continue the approx.

hope this helps:)

Gigi Elizarraras 2C

The 1/2 is from the form 1/a where a is the coefficient of the reactant:) and the rest is just the differential of the reactant over time

hope this helps:)

Gigi Elizarraras 2C

Yes:) I would assume that n=1 for first order reactions, and similarly n=0 for zero order
hope this helps:)

Gigi Elizarraras 2C

To calc the half life use the equation t1/2=[A]0/2k. but you must know the INITIAL concentration:) hope this helps!

Gigi Elizarraras 2C

K is just the Boltzmann constant:) nothing too special as far as I know lol!

Gigi Elizarraras 2C

I think that it is definitely possible to have more than 3, but for this class I'm pretty sure Lavelle will only focus on a max of 3 reactants:) hope this helps!

Gigi Elizarraras 2C

The ln[a] graph will be negatively linear whereas the [a] graph will be exponentially decreasing. Both graphs represent the first order, but it is only the y-axis value that is different

Hope this helps:)

Gigi Elizarraras 2C

I would just look at the flow of the electrons!
Anodes are oxidized and cathodes are reduced:)

Hope this helps!

Gigi Elizarraras 2C

The value of n is going to be the amount of electrons transferred:) you can find this out by doing the redox half reactions!

Hope this helps!

Gigi Elizarraras 2C

Ecell= Ecathode-Eanode

So if there is a greater difference between the two chambers than the cell potential would increase. So it depends on which side the dilution is occurring on.

Hope this helps:)

Gigi Elizarraras 2C

I just like to think of E naught as a constant that does not change for a reaction. And like others have said, it is an intensive property:)

Hope this helps!

Gigi Elizarraras 2C

Hi:)

The salt bridge helps keep electrical neutrality! The positive and negative ions can evenly distribute between the anode and cathode sides.

Gigi Elizarraras 2C

I would also ignore the sign in this case. The question is more so pertaining to the overall value as opposed to the sign of change(+/-)

Hope this helps:)

Gigi Elizarraras 2C

Yes you are correct!:) is there is not delta V then the work would equal zero as work is dependent on the volume of a system changing!

Gigi Elizarraras 2C

Hi:)
delta H is apart of delta U. delta U is the entire change of internal energy of a system/ heat transfer of the system whereas delta H represents the change in enthalpy. Delta U is more overarching of the WHOLE system

Gigi Elizarraras 2C

I do not think that you will be expected to memorize those values, but with anything it wouldn't hurt to know! Cv is usually given from my experience:)

Gigi Elizarraras 2C

https://courses.lumenlearning.com/suny-introductory-chemistry/chapter/spontaneity-free-energy-and-temperature/

This chart really helped me understand:) the big picture is just understanding when the gibbs free energy will be negative(neg=spontaneous)

Gigi Elizarraras 2C

I would first look at what you've been given in the question, what are their units, and what units you need for the answer.
Once you've looked at what you have, try to determine what equations could apply(look at their constants and units necessary)

Hope this helps:)

Gigi Elizarraras 2C

I would just try to remember that work for REVERSIBLE>>>> work IRREVERSIBLE. But while irreversible is faster, it is also less efficient.
Hope this helps:)

Gigi Elizarraras 2C

Use the equation: Cp-Cv=R
hope this helps:)

Gigi Elizarraras 2C

deltaS = q/T for when there is a constant temperature
deltaS = nR*ln(V2/V1) for when there is a change in volume
deltaS = nC*ln(T2/T1) for when there is a change in temp
and remember that Cp-Cv= R

this basically summarizes the last two comments, hopefully this helps:)

Gigi Elizarraras 2C

For changes in entropy think about how much space the molecules will occupy after the phase change compared to the original phase.
For changes in enthalpy think about whether the reaction occurs spontaneously or requires heat to occur.

Hope this helps:)

Gigi Elizarraras 2C

Just look at the GAS molecules when considering the work for this problem:) if there is a net increase of moles of gas on the product side then work is done on the surroundings.

Gigi Elizarraras 2C

I denote work as a lowercase "w" :)

Gigi Elizarraras 2C

The "n" represents the 2 state system, and there are 4 molecules of CO... so you will have N^4 :)

Gigi Elizarraras 2C

I just know the one for acids:
so - sulfuric acid
I - HI
brought -HBr
no - nitric acid
clean - HCl
clothes- perchloric acid

and that, like summer said, the group 1 and 2 elements form strong bases:)

Gigi Elizarraras 2C

If the system does work than the work is negative, but if work is done on the system than that work is positive:) so if there is a larger negative kJ then that system did a larger amount of work .

Gigi Elizarraras 2C

As Hila said above, Lavelle should let us know when KA2 is significant. Otherwise I would assume that only one deprotonization is significant:)

Gigi Elizarraras 2C

When you are unable to find a molecule on the KA chart, start to look for its conjugate base in the KB chart and from there remember that KW=KAxKB. Hope this helps:)

Gigi Elizarraras 2C

Look at the difference in bond stability for the resonance structures(eg double bond kj vs single bond kj):) the structure with the smallest energy I would assume to be the more stable structure!

Gigi Elizarraras 2C

I wouldn't worry about sig figs too much:) with the test being multiple choice and Lavelle never putting any emphasis on sig figs I would just round as you normally do and if you did the calculations correctly there should be an answer very similar if not the same available:)

Gigi Elizarraras 2C

In exothermic reactions, when heat is added the reactants will be favored just because the reaction releases energy when products are formed, so it doesn't need more heat. In endothermic reactions, an increase in heat will favor the products bc these reactions require heat as an energy source, so mo...

Gigi Elizarraras 2C

The larger the Ka the stronger the acid, and conversely, the larger the pKa the weaker the acid:)

Gigi Elizarraras 2C

When a system is disturbed, it will do whatever possible to bring it back to equilibrium whether that be favoring the products or reactants etc. Basically the reaction wants to be balanced again:)

Gigi Elizarraras 2C

The first thing I always do when I see partial pressure is attempt to make an ICE box:) so set it up with:
1 0 0
-2p +p +p
1-2p p p

and then put products over reactants:
(p^2)/(1-2p)^2

Hopefully this is helpful!

Gigi Elizarraras 2C

I would plug it into the KW=[H30+][OH-] equation, but I am not exactly sure if this equation is relevant just because I believe the solution has to be water during the ionization:) let me know how it goes!!

Gigi Elizarraras 2C

I would assume that the calculations would be the same but it is just whether the chemical equation is talking about a acid(ionization) or a base(protonation) as the reactant:)

Gigi Elizarraras 2C

I was confused by this at first too! Basically it is just that because there is so much water as the solvent the concentration of the water barely changes, enough to ignore it! So that is why we consider this change of [H2O] as negligible:)

Gigi Elizarraras 2C

Endothermic reactions require heat to occur so if you makes the surrounding environment hotter, the reaction will become favored and create more product:)

Gigi Elizarraras 2C

That is a really good question... hmm I'm either thinking that is represents the formal charge on the whole molecule or the charge on the element it is directly next to(ex "N").

Gigi Elizarraras 2C

Hi:) to determine the difference you need to be able to identify the reactant as either an acid or base. If the reactant is an acid use Ka and if it is a base use Kb. Hope this is helpful:)

Gigi Elizarraras 2C

I can totally see how they can seem very similar! But to think about their difference just remember that pH refers to the -log[H3O+] and pKA refers to the -log [H3O+][conj base]/[acid]. So basically pH is just taking into account the hydronium concentration.

Gigi Elizarraras 2C

I wouldn't worry too much about the differences between ideal and non-ideal gases because I think in this class we are going to assume all gases we use in calculations will be relevant to PV=nRT. But this seems like a great video if you are looking for a deep explanation: https://www.khanacademy.org...

Gigi Elizarraras 2C

To me Kc makes the most sense so I would tend to use it, but when a problem dealing with gases explicitly gives you partial pressures(atm) us Kp:)

Gigi Elizarraras 2C

Yes you are exactly correct:) reversing the situation(increasing the volume and decreasing the pressure) would turn the reaction to favors the side with a high mole count to balance back out!

Gigi Elizarraras 2C

I would definitely try to use the term favors instead of shifting because it can get a little bit confusing in term of us explaining an equilibrium. And remember as well that when Q<K the products are favored and when Q>K the reactants are favored:)

Gigi Elizarraras 2C

This is a great way to find the y intercepts of the found quadratic equation! Thank you so much! And remember to use the POSITIVE x intercept because concentration is always positive:)

Gigi Elizarraras 2C

For the final I would recommend knowing the order on the spectrum and that visible is light is 400-700nm. and know that the lyman series is apart of the UV spectrum and the balmer series is apart of the visible light spectrum:)

Gigi Elizarraras 2C

this is a bit of a dumb question but what exactly do we mean when we say something is delocalized? i've seen it in a couple of posts and im a bit confused as to what that exactly means When we are talking about delocalization, we are talking about the electrons being free to roam and not stuck on j...

Gigi Elizarraras 2C

You would use the molarities of the products and the reactants so to calculate KA you need to know the concentrations:)

Gigi Elizarraras 2C

[H+] = 10^-pH and then once you have the pH, 14-pH=poH

Hope this helps:)

Gigi Elizarraras 2C

Dr. Lavelle suggests that we treat them both as the same thing:) so [H+] and [H30+] are the same!

Gigi Elizarraras 2C

Yes! We look at bronsted and lewis bases in the same way but it is just the way they are described that differs. Lewis bases are describes in how they donate electrons and bronsted bases receive protons:)

Gigi Elizarraras 2C

The most stable/favorable structures are those with the lowest formal charge and can be found out by drawing the lewis structure:)

Gigi Elizarraras 2C

NH3 is a neutral molecule so it is in turn a neutral ligand. When in doubt draw the lewis structure and calculate the formal charges:)

Gigi Elizarraras 2C

I don't think that we have to remember the exact values for common compounds, but I would definitely not at least that water has a pH level of 7(neutral) and that acids are less than 7 and bases are above 7:)

Gigi Elizarraras 2C

I would still go for either square planar or tetrahedral. We haven't really covered the extent to which to determine between them as far as I'm concerned so I wouldn't worry too much as of now:)

Gigi Elizarraras 2C

The way I typically tell is by looking at the molecule and comparing the distance of the two atoms connected on the periodic table. Atoms close together on the periodic table are typically ionic, and those far away are typically covalent:)

Gigi Elizarraras 2C

Pi bonds are formed laterally so that the molecules cannot rotate. Sigma bonds are formed at the tip so that rotation is allowed. Basically pi bonds make the molecules stuck in position:)

Gigi Elizarraras 2C

In terms of placements, axial bonds are in the vertical plane and equatorial bonds are on the lateral plane. Structures are most favorable when atoms/bonds are farthest away, so I would assume that bonds on the axial plane are preferential because the bond angle is 180 degrees(farthest possible).

Gigi Elizarraras 2C

I would definitely recommend drawing out the lewis structure to see if there are possible resonance structures. If there are then you will have delocalized pi bonds. Better to be safe than sorry:)

Gigi Elizarraras 2C

I first count the number of regions of electron density there are, and then pick the hybridization orbital with that corresponding number of regions. Because sp3 has 4 regions, it is the hybridization for an atom with 4 regions of electron density. And sp had 2 regions, so it must be from an atom wi...

Gigi Elizarraras 2C

I would for sure remember the difference between cations and anions. Cations are positively charged molecules/atoms and anions are negatively charged atoms/molecules. As well as most cations are lewis acids because they are likely to accept electrons and anions are likely lewis bases.

Gigi Elizarraras 2C

To count the number of valence electrons, you would create the lewis structure for the molecule and count how many electrons are attached to the central atom:)

Gigi Elizarraras 2C

To determine the extent of a molecules covalent character, we look at the atoms difference in electronegativities. If molecules have a very close electronegativity then they have a high covalent character. Difference in electronegativity<1.5= covalent.

Gigi Elizarraras 2C

To determine the ionic characterization of a molecule we look at the electronegativity between the atoms. The molecules with the highest electronegativity are those at the top right and lowest and the bottom left. So I would assume that the larger the size difference of the molecules, the more ionic.

Gigi Elizarraras 2C

Lewis acids accept electrons and bases donate electrons. So when you so a molecules lewis structure and see it has lone pairs, it will likely be a base because it has donate them. Also the formal charge helps me decipher(negative=base, positive=acid).

Gigi Elizarraras 2C

As far as the dipole moment, it is the measure of the electric polarity of charges in a molecule(the uneven distribution of charges among elements in a molecule). I am not sure how to calculate the magnitude of each charge, but if you know each charge you can multiply them and then divide by the dis...

Gigi Elizarraras 2C

In ice, the water molecules stay together, and their bonds are then larger than those of the liquid water molecule(broken and unbroken simultaneously. So with the increased distance between molecules, the density is less causing it to float:)

Gigi Elizarraras 2C

5s is the outermost shell in this situation and going to be the shell that the first couple electrons are going to be taken out of despite being first in the periodic table. In general, the NS2 shell electrons will be taken before the ND10.

Gigi Elizarraras 2C

If a molecule has extremely strong intermolecular forces than it must have a high boiling point. The stronger the forces, the more energy needed to break apart the molecule(higher heat=higher energy).

Gigi Elizarraras 2C

I would agree with the others in that bond length plays a major role in determining the bond strength. In the same molecule, a single bond is less strong than a double, and a double weaker than a triple. Atom size also plays a prevalent role in that as atomic radius increases so does the ionization ...

Gigi Elizarraras 2C

Yes! If ml is specified but not ms that is because ms just refers to the spin of the electrons in a subshell. The spin can either be up or down so there are only two options for ms:)

Gigi Elizarraras 2C

I definitely think just doing review problems is the best way to use your time! Getting your mind in the right "chemistry mode" is really helpful to me because honestly sometimes my brain can get pretty overwhelmed, but just taking my time through problems helps me find good strategies of ...

Gigi Elizarraras 2C

The closer the formal charge to 0, the more stable. If the formal charge has a high negativity than the molecule is highly reactive.

Gigi Elizarraras 2C

To find the number of electrons in an atom just look at its atomic number:) because the number of protons in an atom matches the number of electrons. To find the number of valence electrons in an atom just count across the period on the period table!

Gigi Elizarraras 2C

The midterm was posted today with our scores on CCLE in the grades section on the left hand side:) I was not able to look at the problems I missed but hopefully we will be able to whether that be in discussion or if Professor Lavelle releases the test.

Gigi Elizarraras 2C

oh my gosh thank you for putting up this question! It's so important to remember to relax and enjoy the journey however corny it sounds:) To relax I love going outside and backpacking. Even its just for a single overnighter trip, it lets me forget about all my stress and honestly just reminds me tha...

Gigi Elizarraras 2C

The atomic radii will increase as you move down the group because electrons are being added to other shells, and the radii will decrease across a period as an increase in electrons will result in a higher nuclear charge pulling the electrons tighter towards the nucleus. Hope this helps:)

Gigi Elizarraras 2C

I would for sure convert nm to m whenever you have to plug in values to equations. Because meters is an SI unit you must use it in equations to make sure of unit consistency:)

Gigi Elizarraras 2C

C is a constant in the equation such as "h"=6.626*10^-34. So I would continue using the constant as 3*10^8 for the purposes of our use. But as far as momentum equation(p=mv) the velocity changes.

Gigi Elizarraras 2C

Once the last discussion section has completed it the scores will be released I think:) hopefully after we will discuss the questions and get a better understanding of them too!

Gigi Elizarraras 2C

I am not sure if my answer is correct but I am leaning toward "A". Because frequency("v") is related to the speed("c") in the equation c=h*v a decrease in the frequency would result in a decrease in the speed of the radiation. But I am not 100% so if someone could doubl...

Gigi Elizarraras 2C

My TA said that we would be able to use our calculators, formula sheet, periodic table, and scratch paper so I'm assuming that we can get an additional piece of paper. But I'm thinking that they may want to check the front and back of our own scratch paper before we start the exam. Hopefully this is...

Gigi Elizarraras 2C

I think that NaOH is referred to as a formula unit because of its type of bonding(ionic), and similarly H2O is referred to as a molecule because of its molecular bonds. Hope this is helpful:)

Gigi Elizarraras 2C

This statement is FALSE. An increase in intensity will lead to an increase in the number of photons emitted and therefore an increase in the number of electrons affected(1 photon: 1 electron). But the number of electrons affected will not contribute to the total amount of energy, as frequency is the...

Gigi Elizarraras 2C

My TA was telling us that learning too much about the electromagnetic spectrum would definitely be better than the alternative. We won't be given a guide to the EM spectrum so at look getting a rough idea of wavelength and their corresponding regions would be really beneficial. And knowing the wavel...

Gigi Elizarraras 2C

The SI unit for length is meters so when in doubt I would go with that! But in an example problem during lecture, Professor said that both meters and nanometers are acceptable. Unless explicitly specified or needed for specific conversion factors both should work:)

Gigi Elizarraras 2C

Yes amplitude is related to the intensity of the light/photons. The higher the intensity, the more photons affected! But in terms of creating energy to release electrons in the photoelectric effect, increasing amplitude does not increase the likelihood of release:) hope this helps!

Gigi Elizarraras 2C

1/2 mv^2 is the kinetic energy/excess energy of the electron. If the energy to release an electron is less than the energy of the photon, you will be left with kinetic energy that can be calculated with the speed of the electron giving off:)

Gigi Elizarraras 2C

Yep you got it! Like professor was talking about, if you increase the number of runners but no one has enough energy to get over the hurdles you will not get anywhere. If you want a photon/runner to get over the hurdle/release an electron you must increase the frequency not the wavelength:)

Gigi Elizarraras 2C

Most electrons in the Balmer series start at n=3 and go to n=2. The most important aspect of the Lyman series is that there is a much greater energy release as the electron goes from n=2 to n=1, and the "jump" is much larger than from 3 to 2. As the electron levels go higher, the levels be...

Gigi Elizarraras 2C

I asked my TA today that same question, and as far as she knows the lectures will continue to be asynchronous unless explicitly expressed otherwise. But the discussions and office hours will offer the live interaction if you want it!

Gigi Elizarraras 2C

I just completed that question! For this one assume that the equation is balanced and the ratio of the molecules is 1:1. No balancing needed:)

Gigi Elizarraras 2C

If only 1 mole of A is present than you know that the product will have half of the moles it would if you had the 2 moles requires(you only have 1/2 moles of A-> .5). And because you need the same number of moles on the left side(3 moles if you were to have the 1 mole of b and 2 of a), you take half...

Gigi Elizarraras 2C

To start this problem I would calculate how many moles of CaCO3 are produced from the 1 Kg. And knowing that the ratio of CO2 to CaCO3 is 1:1 you know that the moles will be the same for both molecules. Hopefully this is right and helps you out:)

Gigi Elizarraras 2C

The most common times I've used Avogadro's number is when I am finding the number of molecules and converting molecules of elements to moles. In one mole there are 6.022e23 particles/molecules so if you know how many moles of an element there are, then you can determine the number of particles. ex: ...

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