CHEMISTRY COMMUNITY

melissa carey 1f

you can cancel the F

melissa carey 1f

In a TA review session he explained that when you have a rev process you are extracting the max work bc you are making such small changes that you can appoximate P-internal = P-external at every instant. PV=nRT. P=nRT/v. substitute w=-nRT/V and integrate w respect to V. this is where you get w = -nR...

melissa carey 1f

viewtopic.php?f=142&t=30043

melissa carey 1f

viewtopic.php?f=142&t=30043

melissa carey 1f

nucleophiles also usually have a partial - charge like the example from the lecture.

melissa carey 1f

Why are heat and work not state functions? G H and S are all quantities of energy (in the form of heat or disorder) contained within a compound. Work and heat are CHANGES in energy. How you change energy depends on the PATH. your altitude on a mountain = state function = G H S how you got to the to...

melissa carey 1f

You want e- to flow anode to cathode. At the anode Cu(s) > Cu2+ + 2e-. At the cathode Cu2+ + 2e- > Cu(s). So the anode [] is a product and cathode [] is a reactant. Since you want postive E and Q=P/R, so, using the eq, you can see that anode should always have lower [].

melissa carey 1f

viewtopic.php?f=140&t=28119&p=86476&hilit=Porous+Disk+Salt+Bridge&sid=342fa2c635d854d52622ef0dcd9fec62#p86476

melissa carey 1f

I use this:

A---B--C is the transition state since it has a lot of energy, and shows the collision of the particles.

melissa carey 1f

In the question below, each peak is an activation energy of a step in the reaction. The top of each peak represents an activated complex / transition state.

melissa carey 1f

When you ADD heat, ∆H is +. Ex - adding heat to boil water has +∆H, so ∆S = +∆H/T.

melissa carey 1f

W=-P∆V. ∆V = V_f - V_i.

melissa carey 1f

I like to keep this chart in mind.

melissa carey 1f

I attached my work:

I wrote down the potentials for all the possible 1/2 reactions, and found the pair that summed to the most +, since this is a galvanic cell (E>0). Then you just balance and add them. :)

melissa carey 1f

Since total entropy of an isolated system must always increase (2nd law) - then ∆S_tot must always be positive. Order cannot come from disorder without an input on energy. For example, think about freezing ice. Liquid > solid is a decrease of energy, but you must put in MORE energy (electrical from ...

melissa carey 1f

viewtopic.php?f=144&t=28865

hope this helps!

melissa carey 1f

You get a -dG from the two reactions, and this energy is used to drive the ATP production. It's a transfer of energy between two separate entities, so the heat given off by the two reactions is used to make ATP. Like hot water mixing with cold water, the hot water gives off energy and the cold water...

melissa carey 1f

Hi! Is there a relationship between Gibbs energy and activation energy? Thanks! :)

melissa carey 1f

this can be seen in the arrhenius equation:

https://www.chemguide.co.uk/physical/basicrates/arrhenius.html

melissa carey 1f

Christy Zhao 1H wrote:How do you know to use the equation $\Delta U=(3/2)nR\Delta T$ ?

Since its in a bomb calorimeter, the volume is held constant, so c=3/2R for an ideal gas.

melissa carey 1f

You can think of the enthalpy of formation as the heat stored in the bonds of the molecule, formed from its components.

melissa carey 1f

How does the overall rate indicate these relationships?

melissa carey 1f

How does this graphic representation correlate to the presence of a catalyst?

melissa carey 1f

I believe these terms are used to refer to the same reactions as exothermic and endothermic.

melissa carey 1f

Since the rate increase is linear to reactant concentration increase, it implies it's first order.

melissa carey 1f

First order indicates that doubling the reactant concentration doubles the rate because rate = k [A]^1

melissa carey 1f

I thought we only needed to know half-lives for first-order reactions?

melissa carey 1f

∆G is a state function, so you can add them. E_cell is NOT a state function, so you can't simply add them. This is why you have to convert to ∆G and back to E.

viewtopic.php?t=3754

melissa carey 1f

I interpreted it as there is a flow of electrons, which, if put into a circuit, would allow for electric work to be used, despite electrons are flowing cathode to the anode.

melissa carey 1f

Br is the anode since its losing electrons, going from Br- to Br2(l). Br2(l) has an oxidation number of 0, while Br- has an oxidation number of -1. The reverse logic can be used on Hg.

melissa carey 1f

Vincent Chiang 1L wrote:The KOH is there as a salt bridge to allow for the flow of ions.

Thank you! How are we supposed to know its KOH? Is this a common convention, like Pt(s)? Thanks!

melissa carey 1f

Hi! I was wondering why in the solutions manual potassium is included in the final cell diagram? Thanks!

melissa carey 1f

Whats the relationship between free energy and max work - are they equal?

melissa carey 1f

When a problem asks for Gibbs Free energy in "kJ" does this mean kJ/mol or just kJ?

melissa carey 1f

In a battery, like a AAA battery, what serves as a salt bridge?

melissa carey 1f

This isn't what the solution manual says? Can someone explain how to approach this problem?

melissa carey 1f

What is the porous disk composed of? Does it act differently than the salt bridge in any way?

melissa carey 1f

I may be remembering incorrectly, but in high school, I remember one side being negative and the other positive, is this convention used? If so which side correlates to which sign? Thanks!!

melissa carey 1f

The ion which is reduced will gain electrons, and its oxidation number will decrease. On the other hand, the ion which is oxidized will lose electrons and its oxidation number will increase.

melissa carey 1f

Also, when do we need to include n, the number of moles, as I see it omitted in some forms of the equations? Thanks!

melissa carey 1f

We also use P1/P2 as opposed to V2/V1 since pressure and volume are inversely related. P1V1=P2V2.

melissa carey 1f

Additionally, during a process of expansion entropy increases as there are more possible states.

melissa carey 1f

It depends on the type of system the reaction is being carried out in. If the problem specifies that it is isothermal, use Cp. It it is being carried out in isochoric, use Cv. If it is isobaric, use Cp to calculate q because pressure is not changing and change in volume will be accounted for in cal...

melissa carey 1f

To clarify: will irreversible expansion be in test #1? I thought Dr. Lavelle said that it would not be tested, but it appears in the assigned homework problems? Thanks!

melissa carey 1f

To clarify: will irreversible expansion be in test #1? I thought Dr. Lavelle said that it would not be tested, but it appears in the assigned homework problems? Thanks!

melissa carey 1f

Will we be tested on memorizing the formulas in section 8.10: A Molecular Interlude: The Origin of the Heat Capacities of Gases? Thanks!

melissa carey 1f

Hi! I was wondering if we need to know the Equipartition theorem and Degrees of Freedom and the formulas for test 1, as I don't remember going over it in class? Thanks!

melissa carey 1f

This can be seen in the phase change diagram, as the long section during which heat is added to change liquid to gas represents a significant amount of energy. This energy, when transferred to a hand, causes a more severe burn.

melissa carey 1f

Is there a type of system which somehow exchanges particles but not heat? Or is this impossible?

melissa carey 1f

Additionally, it seems, that in the textbook we can usually assume the gas is behaving ideally, unless stated otherwise? Someone correct me if I'm wrong.

melissa carey 1f

Is there another way to determine if a reaction can occur spontaneously?

melissa carey 1f

Is this sheet posted anywhere so we can start working with it? Thanks!

melissa carey 1f

Does anyone know if there is a schedule posted anywhere which outlines which sections of the book correspond to each lecture? Thanks :)

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