CHEMISTRY COMMUNITY

Alexis Sanft 1E

Is water the only thing not included?

Alexis Sanft 1E

I just though that metals were conductive and then nonmetals were not. But if someone else knows more about this I would love to know as well.

Alexis Sanft 1E

When using the pre-equilibrium approximation and there are three steps and the slow step is given, how do you know which fast step to assume is at equilibrium?

Alexis Sanft 1E

Does anyone know how to determine if something is a weak acid or base, or are we just supposed to have a list memorized, and if so how do we obtain that list?

Alexis Sanft 1E

n is found by the number of moles of electrons being transferred. You have to make sure the number of electron transfer is balanced though by balancing both electron count for the half reactions.

Alexis Sanft 1E

From what I understand I'm pretty sure n is just equal to the number of moles of electrons being transferred from the balanced equations. So both half reactions need to be gaining or losing the same amount of electrons, and this is your number of moles.

Alexis Sanft 1E

Catalyst will appear in reactants first and then later in products, so they are first consumed and then produced, so R-->P.
Intermediates will first appear in products, then reactants, so first produced then consumed, P-->R.

Alexis Sanft 1E

What if we missed a week, can we post more this last week and make up those points?

Alexis Sanft 1E

An intermediate will appear first in the products and then in the reactants. It is produced and then used up.

Alexis Sanft 1E

How do you know which one you are looking to solve for? Will it just specifically say it, or is there also some other indicator?

Alexis Sanft 1E

Thermodynamics deals with how favorable a reaction is, whereas kinetics deals with the speed/rate at which the reaction will take place. In reference to the diamond and graphite example that a student mentioned earlier, the reason that people are willing to spend so much on diamond jewelry is that ...

Alexis Sanft 1E

In what scenario does -ΔS surr =ΔS system ? Hi! The scenario in which that statement is true is when delta S universe=0, which is for a reversible reaction because it is slow enough for the surroundings to restore the heat lost by work, therefore making the change in the universe 0. Hope this helps...

Alexis Sanft 1E

The conversion of diamond to graphite is still spontaneous, but you would probably need a catalyst to speed up the reaction to a reasonable amount of time If something is kinetically stable and spontaneous does this mean it is thermodynamically unstable and spontaneous? Or how would you determine t...

Alexis Sanft 1E

Does anybody know if the final is accumulative or not? Also, if so do you know if it will be an even distribution of all the topics or if it will be more about the new stuff we are learning since midterm 2 and a little bit about the previous topics covered?

Alexis Sanft 1E

I definitely recommend going to as many step up sessions as possible, they help a lot. They go through step by step topics and problems having to do with topics. They assign a work sheet and then work through it thoroughly with everyone.

Alexis Sanft 1E

Does this have anything to do with neutralization of a reaction, and if not what exactly is neutralization of a reaction and how do we know what we are solving for in this type of reaction?

Alexis Sanft 1E

Simrah_Ahmed1J wrote:For ΔS...

reversible(isothermal): there is a change in V, no change in T
ΔS= n*R*ln(V₂/V₁)

irreversible: there is a change in T, no change in V
ΔS= n*C_v*ln(T₂/T₁)

So irreversible is never isothermal?

Alexis Sanft 1E

This does not really have to do with state function, but can somebody tell me how disfunction and stability correlate? Does stability increase or decrease with disorder?

Alexis Sanft 1E

I do not remember learning this yet, but that could just be because I have a bad memory. So, if anyone else remember I would like to know as well.

Alexis Sanft 1E

n and m refer to the molar coefficients here, and you multiply that molecules standard Gibbs free energy number by that molar coefficient.

Alexis Sanft 1E

When do we have to worry about Cp?

Alexis Sanft 1E

You definitely are not alone! For me the book questions really help, but also going to office hours with your TA and getting one on one extra practice is also really beneficial.

Alexis Sanft 1E

You generally stick to Kelvin but there was a sapling question that asked for the answer in terms of Celsius, so just make sure you double check to see what the question is actually asking for.

Alexis Sanft 1E

I find its best to make sure all your units line up with the units they give in the equation before doing any calculations, so you don't forget at the end.

Alexis Sanft 1E

To find the surroundings you use the equation Δ Ssurr = −Δ Hsys / T. To find the universe you use the equation ΔSuniv = ΔSsys + ΔSsurr. I hope this helps.

Alexis Sanft 1E

For anyone who assigned the step up sessions, would you guys recommend doing this? How helpful were they with preparing you for the midterm?

Alexis Sanft 1E

I am confused about the difference between q and delta U, because in question 20 on the sapling assignment they were equal to each other? Was that for a specific reason, or will they always be equal to each other?

Alexis Sanft 1E

I was also confused on this problem. Are we just supposed to know the conversion factors for ice in an enthalpy fusion problem?

Alexis Sanft 1E

I was just wondering, how we are supposed to know if something is a an atom, linear molecule, or nonlinear molecule, like those pertaining to question 20 on the sapling assignment, that were used to fid the heat capacity?

Alexis Sanft 1E

The question gives you your Cp value, its the constant pressure for the specific heat, mine was 5R/2. In order to find Cv you do Cp-R, so for me I did 5R/2 - R= 3R/2 or 1.5R. I hope this helps.

Alexis Sanft 1E

Is there some sort of rule for knowing if something is a strong or weak acid or base, besides pH values, or do you kind of just have to memorize strong acids and bases?

Alexis Sanft 1E

Do standard enthalpies ever change, or are they always the same for a specific molecule no matter the reaction?

Alexis Sanft 1E

Are the only possible changes of substances those of gas, liquids,and solids converting into one another? Are there any other ones?

Alexis Sanft 1E

If the enthalpy of the reaction is positive, then you know the reaction is endothermic and requires energy. This also means that since the reaction is endothermic and requires energy, then an increase in temperature will lead to your K value increasing, essentially making Q<K, and causing a shift to...

Alexis Sanft 1E

the equation for work is w=−PΔV and work is being done when w is negative. That means in order for work to be done ΔV must be a positive value. So we know work is being done with the volume increases in a chemical equation. You can figure this out by looking at the moles in the reactants versus the...

Alexis Sanft 1E

Does anyone know if Lavelle is also strict on significant figures? I just want to make sure that I do not loose easy points on the midterm, so if anyone who has taken him previously could say, I would appreciate it!

Alexis Sanft 1E

Closed systems have a fixed amount of matter and allow the transfer of energy as heat. Volume can actually be changed in such a system but it would most likely be as a result of a change by the experimenter such as moving a piston up or down to change volume and pressure. So, does the transfer of e...

Alexis Sanft 1E

A lot of the problems give a temperature in them, but I don't know when we have to take it into account and when we don't. When reactions take place at the same temperature, like for example in #7 and #8 on the Week 2 Sapling the Ka and Kb take place under the same conditions, I've been told we can...

Alexis Sanft 1E

Also, do we need to do any actual calculations if the pkA is given and the pH is given?

Alexis Sanft 1E

What does it mean to be a "predominant" species?

Alexis Sanft 1E

Do any of you guys know if we are expected to know if something is a weak or strong base off of memorization for the midterm?

Alexis Sanft 1E

Does anyone know when the Chemistry Community posts are supposed to be done by each week? I know we are supposed to have posted five times each week, but what day are our posts actually due?

Alexis Sanft 1E

As someone who didn't take 14A with Lavelle how is the midterm formatted? My TA told us we will be in a zoom room with our TA and it will be administered over respondus and it will be multiple choice. We will be able to use a calculator and are expected to show our surroundings. I hope that helps. ...

Alexis Sanft 1E

For the exam do you guys know if we will be tested on endothermic and exothermic reactions, like will we have to know if a reaction is endothermic or exothermic?

Alexis Sanft 1E

Shreya Patel- 2D wrote:What's the difference between protonation and ionization then?

Does anyone know if we are supposed to have already learned this and if there will be questions on this on the exam?

Alexis Sanft 1E

When working with acids and bases and conjugate acids and bases, will the acid or base always be on the reactant side of the reaction being formed and the conjugate acid or base always be on the product side?

Alexis Sanft 1E

Hi, I was wondering how you know in an equation which one is the base and which one is the acid, and if we are expected to know how to figure that out or if it will be stated in a problem?

Alexis Sanft 1E

I learned from last quarter to spread out my studying and to avoid cramming in this class. Attending workshops and step-up sessions throughout the quarter is really helpful for staying on top of information. Using outside resources such as Khan Academy is also really helpful! Hi I was wondering wha...

Alexis Sanft 1E

Hi, the easiest way I think to approach this problem is to combine the formulas that make up the reaction given, by putting them on top of one another, then cancel out any repeating terms that appear on the reactant side of one of the combined formulas, and the product side of the other in which aft...

Alexis Sanft 1E

Hi, I was wondering if anyone knew if the Sapling questions were due this coming Sunday as in three days from now, or if it is due next Sunday as in a week and three days from now. I know Sapling says that the first assignment is due Sunday of week 2, but I did not want miss anything, so if someone ...

Alexis Sanft 1E

I purchased the sapling+ 7th edition ebook a few days ago from ucla and have not received a notification for the prepaid code to access sapling. Does anybody have a solution or are in a similar situation? Thanks. Hi, I had the exact same problem, because I did not previously take 14A with Lavelle. ...

Alexis Sanft 1E

I am not sure if anyone has already covered this, but regarding what is due on Sapling, are the problems posted on Sapling the only problems each week that we are graded on? I know you are supposed complete the assigned work each week, but are the additional practice problems from the textbook just ...

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