CHEMISTRY COMMUNITY

vibha gurunathan 1h

acids/bases!

vibha gurunathan 1h

strong acids/bases dissociate completely; in contrast, weak acids/bases only partially dissociate, so you'd have to use the ka/kb value to figure out pH, concentration, etc.

vibha gurunathan 1h

only good thing to come out of the coronavirus are memes like this

vibha gurunathan 1h

for gases and aqueous substances you use concentrations

vibha gurunathan 1h

sorry to ask this because I know Professor Lavelle's been working on the easiest/simplest way for us to take the final, but I was wondering whether we just submit the answers on the final exam? or do we have to write out the work on CCLE? If not, are we still able to get partial credit or is it all ...

vibha gurunathan 1h

I'm pretty sure it's going to be the same timeframe as the normal final.

vibha gurunathan 1h

In addition to what everyone else said, it also includes certain elements that exist in their normal state in multiples (like P5)

vibha gurunathan 1h

Sidharth D 1E wrote:To expand on that, reactions that give a straight line when lnk_r is plotted against 1/T are said to show Arrhenius behavior

What is arrhenius behavior?

vibha gurunathan 1h

Thanks so much Lyndon! Your review sessions and worksheets were incredibly helpful!

vibha gurunathan 1h

Do you know if chemistry community will be locked while we take the final?

vibha gurunathan 1h

Diana Chavez-Carrillo 2L wrote:Does anyone know when we will be given our take-home final? Is it still going to be on Sunday?

I think it's still going to be sunday, as there's nothing to indicate otherwise

vibha gurunathan 1h

Philip wrote:How are you guys going to be studying for the final

I'm planning to look over the study guide Dr. Lavelle sent out, do the endgame worksheet Lyndon posted, and review my notes/ do practice hw problems.

vibha gurunathan 1h

Clara Cho 2K wrote:Do you think we will still meet for discussion?

I don't think so, I'm pretty sure we just email our hw in

vibha gurunathan 1h

Catalysts create an alternate pathway - they speed up reactions by lowering Ea.

vibha gurunathan 1h

I'm pretty sure either work

vibha gurunathan 1h

In my notes, 'A' is defined as the frequency factor or pre-exponential factor (including # of collisions with correct orientation). What does this mean? Is this what we're trying to calculate with the Arrhenius equation? I'm pretty sure it's given. From what I remember in class, Dr. Lavelle said it...

vibha gurunathan 1h

Besides adding a catalyst, can increasing the temperature, increasing pressure, or decreasing volume speed up a reaction with the large activation energy? I'd assume that it would change the reaction forwards/backwards in terms of Le Chatelier's Principle? but I'm honestly not too sure how it inter...

vibha gurunathan 1h

The pre-equilibrium approach says that the intermediate is formed and sustained in a rapid formation reaction and its reverse, and you assume it reaches a sort of equilibrium. Instead, the steady state approach assumes that concentrations of the intermediates are low and don't change. As you don't w...

vibha gurunathan 1h

K and temperature are proportional, so increasing temperature also increases k (increasing your rxn rate)

vibha gurunathan 1h

Dear Dr. Lavelle,

Thank you so much for all the work you put into teaching us this quarter! I really appreciate all the effort you put into lectures and organizing our review sessions, and I learned so much.

vibha gurunathan 1h

The intermediate is formed and used up, and it doesn't appear in the overall chemical equation

vibha gurunathan 1h

I'm not completely sure, but I think Gibb's free energy is usually given in kJ/mol and delta H is given in J/mol. To be honest, though, I think either would work as long as it's the right one for the problem/right one with the information given

vibha gurunathan 1h

005162520 wrote:Is the second step our first step and the second step or fast step?

I'm pretty sure it's when the second step is slow, so it limits how fast the first step can go

vibha gurunathan 1h

Rida Ismail 2E wrote:My guess is there will probably be an online alternative. I'm sure that Dr. Lavelle will send out an email in the next few hours about what he is going to do about finals.

Gotchu, thanks!!

vibha gurunathan 1h

I know the news just broke, but does anyone know how the final is going to work?

vibha gurunathan 1h

You determine the order from experimental data - the method usually depends on the information given in the problem.

vibha gurunathan 1h

Does anyone know when the best time to start preparing for the MCAT is? This is something that depends on each individual. Some people try to study while still taking classes. I took a gap year where I studied for the MCAT and did more clinical work. It's completely up to you. What's important to k...

vibha gurunathan 1h

Thank you so much for creating this!!

vibha gurunathan 1h

KatrinaPho_2I wrote:If you look up the worksheets that the TA Joyce posts on chem community, they are really helpful. Lyndon's review sessions are also very helpful.

how do you look up the worksheets?

vibha gurunathan 1h

I'm pretty sure Professor Lavelle makes it.

vibha gurunathan 1h

in addition to what everyone else said, elements in their standard state have an oxidation number of 0 (so like O2 would have an oxidation number of 0 or H2 would have an oxidation number of 0)

vibha gurunathan 1h

How is delta H impacted when the system's at constant temperature and pressure?

vibha gurunathan 1h

If a reaction is compressed, I know that it goes to the side with less molecules of gas, but I don't remember the explanation he used in class. Could someone explain that?

vibha gurunathan 1h

Does anyone know when the best time to start preparing for the MCAT is?

vibha gurunathan 1h

If you add a solid product/reactant, does the reaction shift? (b/c it isn't in the K expression)

vibha gurunathan 1h

- if delta H is negative and delta S is positive, Gibbs Free energy is negative (spontaneous) - if delta H is positive and delta S is positive, T(delta S) has to be greater than delta H for Gibbs Free energy to be negative - if delta H is negative and delta S is negative, delta H has to be larger th...

vibha gurunathan 1h

Gases have their molecules a lot more spread out, liquids are only slightly spread out, and solids have their molecules tightly packed.

vibha gurunathan 1h

Why is Cpm (5/2)R and why is Cvm (3/2)R?

vibha gurunathan 1h

Ruby Tang 2J wrote:In the relevant section of the textbook, it is explained that for a monatomic ideal gas, Cp = 5/2R, while Cv = 3/2R, where R = 8.3145 J*K-1*mol-1.

Do you know if we'd need to know this on our test, or if they'd give us these values?

vibha gurunathan 1h

Inert gases don't react with any of the reactants or products.

vibha gurunathan 1h

It depends on the units of the constants in the problem. If it's a problem with molar heat capacity, use kelvin. If specific heat capacity, you would use celsius. Furthermore, usually you'd do delta T, which either would work. The ideal gas law, however, is always in kelvin, and usually if they ask ...

vibha gurunathan 1h

Increasing the amount of intermolecular forces causes more deviations from ideality, so gases that have a larger molar mass would be less ideal that gases with a lower molar mass. (E.g. CO2 would be less ideal than He)

vibha gurunathan 1h

Adding on to that, most gases are not "perfectly" ideal but they're close enough to the ideal. Gases with large volumes, a high pressure, or a very low temperature can cause deviations from this ideal.

vibha gurunathan 1h

Use the concentration's (you can still use concentrations for gases).

vibha gurunathan 1h

Only temperature can change K. (Pressure, volume, etc. can change the concentrations of reactants/products, but cannot change the equilibrium constant).

vibha gurunathan 1h

Ka greater than 10^3 signifies a strong acid. Ka = [CB][H+]/ [HA] The more the acid (HA) dissociates, the more H+ is produced. This increases the Ka because the concentration of the products increases. If the Ka is greater than 10^3, that means it dissociates a lot, making it a strong acid and not a...

vibha gurunathan 1h

Alexaaguilera wrote:I think you only include gases when doing an ICE

you include gases as well as aqueous reactants/products

vibha gurunathan 1h

They don't react with either the reactants or products, so it does not shift equilibrium in either direction.

vibha gurunathan 1h

I don't think there's a part c for 6B.3. Maybe it's a different problem that you're looking at?

vibha gurunathan 1h

The formula's the same and you find it in the same way, but you use current concentrations/pressures for Q and equilibrium concentrations/pressures for K.

vibha gurunathan 1h

It tells you relatively how much of the products or reactants are made. If Q is smaller than K, you don't have as many products made, so the reaction progresses forward to make more products to make Q larger and reach the value of K. If Q is larger than K, it will proceed in the direction of the rev...

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