CHEMISTRY COMMUNITY

JosephineF

If you are able to do the in text problems then you should be good. He often wouldn't cover certain topics that we ended up needing to know in lecture but everything you need to know is in the text book.

JosephineF

Treat it like the SAT. Every question is weighted roughly the same so do a once over where you answer everything you know off the top of your head. Then go back over and spend some time with the ones you skipped. Then go over it one last time to check that you did them all correctly and didn't make ...

JosephineF

Jose Robles 1D wrote:Wait is the whole test going to be on CCLE now right?

I believe so yes

JosephineF

The catalyst is not created by the reaction but is also not present in the final balance equation because it gets canceled out. An intermediate is essentially the same except it is created by the reaction and is then used up and canceled out by the next mechanism. So it too is not in the final balan...

JosephineF

What are the units for A? Also is it a numerical value? All I really know is that it relates to the frequency and orientation of collisions

JosephineF

A is the frequency factor so it includes the frequency and orientation of collisions

JosephineF

probably when given some sort of mechanism you would need to be able to tell the difference between a catalyst and an intermediate. So the catalyst is not created but the intermediate is created and then is then used.

JosephineF

I've seen a version of the Arrhenius equation that looks like: $ln(k_{2}/k_{1})=-E_{A}/R(1/T_{2}-1/T_{1})$ . I'm guessing it's used for finding one temp or the other but wouldn't that mean you would have to be given both ks?

JosephineF

Will have to actually do integrals and derivatives or was that just used as showing us conceptual why the equation works?

JosephineF

How everyone is about to be with spring quarter online classes

JosephineF

we're all gonna be this cool after we finish this final

JosephineF

I've been putting my phone on do not disturb and setting a timer for an hour at a time and so for that I hour I sit and study and then when the timer goes off I give myself a 10 minute break and then I restart the timer for another hour. You just have to get into a groove. The hardest part is starti...

JosephineF

Will translational and rotational contribution from molecular motion be on the final? I don't ever remember covering it in class but it is in some of the 4C homework problems

JosephineF

I think he said he is going to send a more detailed email about logistics later this week

JosephineF

On the last slide of Lavelle's review it asks to choose which students' mechanism is valid based on the observed rate law. I'm not sure where the K1,k1, and k2 are coming from and how they are used to determine the rate limiting step. If someone doesn't mind walking me through that whole problem, it...

JosephineF

In Lavelle's review slides there is a problem asking what the problem is with the cell diagram and the correction is the addition of Pt(s) to the right side. Is this because the right side only had Br(aq) and Br(g) and there needs to be a solid conductor in a galvanic cell?

JosephineF

In Lavelle's review there is a problem talking about calculating the Gibbs free energy under non equilibrium condition and in the end \Delta G is positive. The slide says that because it is positive the reaction is spontaneous. I thought in order for a reaction to be spontaneous \Delta G had to be n...

JosephineF

What equation is the solution manual using to solve what the final temp of 50.7 g of water at 22C is after adding 20g of copper at 100C? assuming no energy is lost to surroundings

JosephineF

Why does this problem use $w=-P\Delta V$ for an irreversible expansion but w=-nRTln(V2/V1) for a reversible expansion?

JosephineF

A piston confines 0.200 mol Ne(g) in 1.20L as 25C. The gas is allowed to expand through an additional 1.20 L against a constant pressure of 1.00 atm

How do we know that the expansion of the piston is irreversible expansion?

JosephineF

Should we use the 14A section on Acids and Bases for our questions? I am confused about Q3D of the midterm where it asks: at pH 6, what is the net charge of acetic acid, pKa= 4.75? At the review the TA said that you can tell that it will be a -1 charge because the pKa is smaller than the pH. I am co...

JosephineF

Will we have to know how to do the derivations of integrated rate laws for the test?

JosephineF

Will we always be given the order of the reaction because it has to be determined experimentally?

JosephineF

The stated short hand for the reaction in the text is M\left | M^{+} \left \| Cu^{2+}\left | Cu But in the solution manual says it's Cu\left | Cu^{2+}\left \| M^{2+}\left |M This affects which element is considered the anode and which is considered the cathode but I'm unclear as to why they reversed...

JosephineF

given the equation $2Ce^{4+}+3I^{-}\rightarrow 2Ce^{3+}+I_{3}^{-}$ how can you tell how many moles of electrons are being used?

JosephineF

they also omit oxygen from the calculation of $\Delta G$ but not from the calculation of $\Delta S$

JosephineF

when finding the \Delta H of the reaction 2H_{2}O_{2}(l)\rightarrow 2H_{2}O_{2}(l)+O_{2}(g) is oxygen not included because it is a gas? Are gases never included in enthalpy formations? Or am I just misinterpreting the solution manual's omission of oxygen in the enthalpy forma...

JosephineF

it is asking to write the balanced formation reaction for NH3. The solution manual says 1/2N2 + 3/2H2 --> NH3. Is there a formula for how to arrive at these numbers or is it just guess and check? I'm confused as to how 2 Ns goes to only 1 N and how H2 gains another H

JosephineF

the two equations are: a) MnO_{4}^{-}+S^{2-}\rightarrow S+MnO_{2} b) [Pb(OH)_{4}]^{2-}+ClO^{-}\rightarrow PbO_{2}+Cl^{-} it asks for the oxidizing agent, the reducing agent, and the balanced equation of each. I'm mostly confused on how to determine the oxidation states so that I know which e...

JosephineF

I'm having trouble determining the oxidation numbers in order to determine how many electrons are being exchanged for both a and b. I know this is like step 1 and pretty basic stuff but I haven't taken chemistry in 5 years and I was never totally comfortable with this topic anyway. Any tips would be...

JosephineF

for all your extermination needs

JosephineF

chem final outfit ideas

JosephineF

why is D correct if it is +23 and the given enthalpy is negative? Even when you divide by the number of moles shouldn't it still be negative?

JosephineF

given the ratio of concentrations how do we know that the hydrogen bromide salt remains pronated?

JosephineF

how to do you know the net charge of an acid given the pH and the pKa?

JosephineF

I had the same question. but I guess if it's a typo then it makes sense. If there were to be Cl2 on both sides of the equation would it be solvable?

JosephineF

does anyone know when Lavelle himself holds office hours? I can't find it on the course website. im sure it's somewhere in plain sight but Im just having trouble finding it

JosephineF

does Lavelle grade on a curve?

JosephineF

for number 7 I understand how to solve for q but how do you solve for w with so many missing variables from the pv=nrt equation?

JosephineF

does anyone know how many questions there will be on the midterm? or what the general set up will be?

JosephineF

what is the difference between extensive and intensive properties?

JosephineF

as long as our units are consistent does it matter if we use kJ or J when talking about enthalpy or entropy?

JosephineF

just confirming there is no class Wednesday of the midterm?

JosephineF

Does anyone know the formula for finding the heat capacity or the specific heat capacity when it is not specifically given in the question?

JosephineF

Does anyone have a deeper explanation for why we would divide ΔG by T for the equation -ΔG/T= -ΔH/T + ΔSsys? In lecture I didn't understand what the purpose was for doing this.

JosephineF

or Gibbs free energy, because it is also assigned as reading but we haven't covered it in class yet

JosephineF

does anyone know potentially how much about entropy of state changes we will have to know for the midterm? It's part of the textbook readings but we haven't talked about much in class yet.

JosephineF

Does anyone know why in some sapling problems of assignment 3 the equation for q is q=nCdeltaT and then other times its just q=CdeltaT? They remove the quantity of the substance in some problems but im having trouble finding out why they do that.

Thanks!

JosephineF

I think this was in reference to the heating curves. My understanding is that if you to take the temperature of the boiling water it would remain the same temperature until there was a phase change even though you are continuing to add heat to the substance in order to induce said phase change.

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