CHEMISTRY COMMUNITY

Dylan Mai 1D

I believe galvanic and voltaic cells are the same thing

Dylan Mai 1D

I think if it were not at equilibrium they would ask you to calculate Q

Dylan Mai 1D

Oh man What did i just watch

Dylan Mai 1D

Yes we should know how to balance equations in basic conditions as well as acidic

Dylan Mai 1D

Yes i think so because there is work being done against a constant external pressure, and therefore that equation is able to be used

Dylan Mai 1D

Yes also another reason is that anything he lectures on has the possibility to be on the final

Dylan Mai 1D

Water is no longer the solvent, which means it is no longer in large excess, and therefore is included in the rate law

Dylan Mai 1D

I do not think you have to convert to the standard mol.L^-1 unless the question explicitly asks. The book leaves it in other units in the answers if thats how the units were originally presented in the question I think

Dylan Mai 1D

Elements that have higher oxidizing power are more easily reduced, meaning they have a higher value of E naught. So you would look at the given values of E naught for each one, and the one with the highest value is the best oxidizing agent

Dylan Mai 1D

The way to find out which reactions to work with is only through looking at the experiments and finding experiments where one concentration changes and everything that is needed to be held constant is held constant. The book uses experiments 2 and 3 because only the concentration of B is changed her...

Dylan Mai 1D

Will we ever need to graph on a test?

Dylan Mai 1D

Although usually, you report the rate as positive

Dylan Mai 1D

Will we start working with catalysts directly in problems relating to kinetics in this class?

Dylan Mai 1D

It is spontaneous when cell potential is positive and not spontaneous when cell potential is negative

Dylan Mai 1D

For if a metal will dissolve, my TA said that would have to do with comparing the E naught of the metal to the E naught of water. The one with the higher E naught will be the one reduced or dissolved. It has to do with question 14.57

Dylan Mai 1D

“A tin electrode in 0.015 M Sn(NO3)2 (aq) is connected to a hydrogen electrode in which the pressure of H2 is 1.0 bar. If the cell potential is 0.057 V at 25 °C, what is the pH of the electrolyte at the hydrogen electrode?” Can someone explain the assumptions made in the solutions manual for this qu...

Dylan Mai 1D

How do you know whether it’s acidic or basic? And then from there how do you know what phase it’s in?

Dylan Mai 1D

14.29 says “Suppose that each of the following pairs of redox couples is joined to form a galvanic generat3 a current under standard conditions. Identify the oxidizing agent and the reducing agent, write a cell diagram, and calculate the standard cell potential. part a: Co 2+/ Co and Ti 3+/ Ti 2+“ H...

Dylan Mai 1D

Are we expected to know how to answer this question without appendix 2B? The question is “write balanced half reactions for the redox reaction of an acidified solution of potassium permanganate and iron (III) chloride”

Dylan Mai 1D

How do you know that the Anode reaction is AgBr + e- to Ag (s) + Br - and not Br2 + 2e- to 2Br-?

Dylan Mai 1D

In this question, Cl2 is reduced to 2Cl-, but in the cell diagram, Cl- is written before Cl2. Why? Thank you!

Dylan Mai 1D

It could be that they go through many reactions or maybe it has to do with things like capacitors being in series or in parallel

Dylan Mai 1D

I would guess that magnitude is something like their voltages

Dylan Mai 1D

do you have an example of one of the problems that does this?

Dylan Mai 1D

does he not bruin cast?

Dylan Mai 1D

have we learned any concepts where acidic or basic affects our calculations of enthalpy, entropy, or Gibbs free energy?

Dylan Mai 1D

is there an entropy of fusion?

Dylan Mai 1D

Why can we not use the given delta S values in appendix 2A in this question?

Dylan Mai 1D

what are the units for delta S? sometimes it is per mol and sometimes it is not. I assume this depends on the question?

Dylan Mai 1D

I remember Lavelle answering a question in lecture about how even if the temperature raises, the difference (delta H) between the same reactants and products stays the same. Their individual enthalpies change, the difference between the enthalpies is for the most part the same

Dylan Mai 1D

I think Lavelle will address this more next week, but my TA said everything we have done so far will be on the midterm, and electrochemistry might be on the midterm

Dylan Mai 1D

do we get to keep our finals or do we have to stay there, view it, and then return it?

Dylan Mai 1D

This formula may also be on the formula sheet when you need it for future tests

Dylan Mai 1D

Can someone also explain what an isobaric reaction is?

Dylan Mai 1D

I think they are just are experimentally found molar heat capacities for mono atomic gasses. They are also on the formula sheet that’s given

Dylan Mai 1D

A technician carries out the reaction 2SO2(g) + O2(g) —> 2SO3 ... In part E, after we have calculated the enathaloy if the reaction and want to find out how much enthalpy has been exchanged, why do we only use the 0.030 mol of SO2 that’s been consumed to calculate the enthalpy if 0.015 mol of O2 was...

Dylan Mai 1D

I think for something like this we would be provided values

Dylan Mai 1D

I believe you know because they say assume that krypton behaves as an ideal gas, and therefore you would have to use the constants 5/2R and 3/2R which are molar heat capacities

Dylan Mai 1D

Honestly for this class it is best to just be safe to know all of them unless Lavelle or a TA said a certain topic or question was not going to be tested

Dylan Mai 1D

so when using delta H, is it wrong for someone to refer to that as heat? delta H is enthalpy right?

Dylan Mai 1D

Question 53 Part B: the reaction of 1.40 g of carbon monoxide with excess water vapor to produce carbon dioxide and hydrogen gases in a bomb calorimeter causes the temperature of the calorimeter assembly to rise from 22.113 degrees C to 22.799 degrees C. The calorimeter assembly is known to have a t...

Dylan Mai 1D

Is it the same constants and equations sheet as 14A?

Dylan Mai 1D

Are we supposed to know the specific terms for those phase changes listed above? Like fusion for example

Dylan Mai 1D

We only need to know this concept, not that actual values for this correct?

Dylan Mai 1D

There are 3 methods we know of right now correct?

Dylan Mai 1D

So if I was in 14A with Lavelle and already have a chem community account registered, do I need to re-register for 14B if I have the same discussion section?

Dylan Mai 1D

the answer to [Co(CN)5(OH2)]2 is aquapentacyanocobaltATE (III) ion. How do you know when there is an -ate attached at the end vs when the ending to a compound name is simply cobalt?

Dylan Mai 1D

On the test, will we have to draw 3D structures and if so, how do we know when to draw one as opposed to drawing a 2D lewis structure? The textbook questions do not really specify when they want a 2D or a 3D structure, but the solutions manual sometimes has 3D structures instead of 2D structures.

Dylan Mai 1D

Will we be asked on the test to answer with the number in front of the hybridized orbital?

Dylan Mai 1D

Question 4.25 D asks for the lewis structure of SF4 and whether it is polar or non polar. In my solutions manual , it shows the lewis structure for SCl4. I know that this does not change the answer of polar or non polar, but wanted to check that the solutions manual shows the wrong lewis structure. ...

Dylan Mai 1D

On question 4.17 it asks for the bond angles in ozone and the azide ion, and gives their respective formulas. will we ever be asked a question that doesn't provide the formulas?

thank you!

Dylan Mai 1D

On question 4.3b, it asks to draw and name the shape of CH2F2. How do you know if the atoms are coming in or out of the page, and how do you know that in this molecule, the hydrogens are the ones going in and out of the page?

thank you!

Dylan Mai 1D

Question shows two ball and stick diagrams for two molecules. One has an angle of 120 degrees and the other is linear with an angle of 180 degrees. It then asks whether there must be, may be, or cannot be one or more lone pairs on the central atom. How can you determine this with this info? thank you!

Dylan Mai 1D

we would just label the single, double, or triple bonds as sigma or pi bonds if asked right

Dylan Mai 1D

I usually keep units our of my calculations unless there are necessary conversions I need to do, and then I make sure to have correct units on my final boxed answer

Dylan Mai 1D

the deltav is just (1.5+0.4)-(1.5-0.4). You could use the 1.5 in this calculation, or disregard it and just double 0.4 for your delta v

Dylan Mai 1D

how do you figure out the charges on the atoms?

Dylan Mai 1D

How do you know the charges for the elements? memorization?

Dylan Mai 1D

What exactly is Z subscript eff? I read about it in the textbook and still don't understand. Was it covered in lecture? I do not see it in my notes.

Dylan Mai 1D

Does anyone have an answer for the question above yet? I also do not remember seeing this formula in lecture

Dylan Mai 1D

Regarding periodic trend exceptions, at a peer learning session I learned that carbon and oxygen are exceptions to e- affinity and ionization energy respectively because carbon wants to gain 1 e- to have a half filled 2p and oxygen wants to lose an e- for the same reason

Dylan Mai 1D

What are the homework problems exactly for this next test and material we are learning? Is it the rest of the Quantum World questions from the syllabus?

Dylan Mai 1D

24 is A, Ultraviolet. I think I got this from my notes or one of the videos, but it also makes sense to have UV light be commonly used since it may have a better chance at ejecting electrons with its higher energy.

Dylan Mai 1D

I believe 22 is A. If no electrons are ejected than that means there is not enough energy to eject the electron. To increase the energy, using a shorter wavelength/ higher frequency would increase the energy and potentially gain enough energy to eject an electron. E=hv, so with a higher frequency co...

Dylan Mai 1D

my TA said a good way to remember how ultraviolet is next to visible light on the 400nm side and how infrared light is on the 700nm side is by just looking at the names themselves. Ultraviolet is next to the violet side of visible light and infrared light is on the red side of visible light

Dylan Mai 1D

The wavelength values of the Balmer and Lyman series are something we should know for the test right? We are not given a spectrum if a question asks correct?

Dylan Mai 1D

Oh i see that we would just count the number of each element that appears in the molecular structure but how do we know the order of the elements in the formula? How do we know it is C10H16O instead of OH16C10? Thanks!

Dylan Mai 1D

For F.1 we are given the molecular structure for Citral and we need to write the molecular formula from that. Is this something we need to know for the test friday and how do we do this question if so? Thank you!

Dylan Mai 1D

I haven't seen anyone talk about this or maybe I missed the post, but on Lavelle's website there is a Sig Fig review document posted under the Text and Exam Schedule and the Solution Manual Errors link that helped me review Sig Figs!

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