CHEMISTRY COMMUNITY

Cynthia Ulloa

does anyone know if we used the steady state approximation or was it just the pre-equilibrium approximation?

Cynthia Ulloa

intermediates are produced and then used up in another reaction. a catalyst appears at the beginning and then again at the end. A catalyst can also be a part of the rate law while an intermediate can't.

Cynthia Ulloa

When setting up our rate rations to find the order of reaction, does it matter which rates we take from the experimental data? and how do we decide which to put as our numerator?

Cynthia Ulloa

If the volume increases, the pressure with decrease and it will shift to the side with more moles. If the volume decreases, the pressure will increase and there will be a shift to the side with less moles.

Cynthia Ulloa

On test 2, there were a few questions that asked us to rank the given species in order of increasing oxidation power going from second oxidation state to neutral. Can someone explain how I would go about this?

Cynthia Ulloa

what is a concentration cell and can you give an example please? I want to get a better understanding

Cynthia Ulloa

Why does steam at 100ºC cause a worse burn than boiling water at 100ºC?

Cynthia Ulloa

Also for cell diagrams don't forget to include the H+ as well!

Cynthia Ulloa

can someone explain what the difference between a regular calorimeter and a bomb calorimeter is?

Cynthia Ulloa

How do we describe the stability of reactants and products when we look at which reaction is favored?

Cynthia Ulloa

I am looking over my Test 2 and I realized I made a couple of mistakes when calculating for Eºcell. I just want to get clarification on whether we switch the sign of a reaction when we flip it in order to use Eºcell = Eºcathode - Eºanode?

Cynthia Ulloa

I am still confused on how we can use ratios when working with rate laws. Can someone give me an example of how we would set this up?

Cynthia Ulloa

Use Ecell= Eº(cathode) - Eº(anode) and you might have to flip one of the equations. I believe the professor will provide us with the sheet that has the E values for each half reaction so you would just plug in accordingly.

Cynthia Ulloa

No, I just think you need to be able to understand the equations and how to use them

Cynthia Ulloa

Can someone explain to me why we would use ln[A] instead of [A] like we do for the rest of the orders?

Cynthia Ulloa

I am having trouble finding the oxidation numbers from elements. Can someone explain to me how we find them? I know there are a few rules, but I am still confused

Cynthia Ulloa

Can someone explain how we read the total charges on the reactions and when we would need to add electrons to either side?

Cynthia Ulloa

How is the stability of a reaction related to its spontaneity?

Cynthia Ulloa

Can someone explain to me what the purpose of platinum is? And how do we know when to use it?

Cynthia Ulloa

When writing our half reactions, will our oxidized reaction always have the e- on the right side? and the reduction reaction will have the e- on the left?

Cynthia Ulloa

Can someone re-explain to me the purpose of a salt bridge?

Cynthia Ulloa

Will the structures be given to us on the midterm or are we expected to know how to draw them?

Cynthia Ulloa

Can someone explain why solutions of weak acids have a higher pH?

Cynthia Ulloa

How do we determine which molecules will have a higher molar entropy? and what is residual entropy?

Cynthia Ulloa

Andre_Galenchik_2L wrote:Don't we need to know that the Cp for a single atom is 5R/2 and the Cv for a single atom is 3R/2?

Yeah, that is what I thought as well

Cynthia Ulloa

There are a few homework problems where we have to make several chemical reactions to solve for Hess's Law. Will we be expected to know how to make them or will the test provide them for us?

Cynthia Ulloa

whitneyhawthorne_2C wrote:Understanding it would definitely make problem solving easier so I would try to as much as you can. I took some notes in my discussion with the graph labeled, a picture of it is shown below. Hope it helps!

thank you so much!

Cynthia Ulloa

"A 50.0-g ice cube at 0.0 degree C is added to a glass containing 400.0 g of water at 45.0 degree C. What is the final temperature of the system (see Tables 8.2 and 8.3)? Assume that no heat is lost to the surroundings." Can someone tell me how to go about this problem? I know we will have...

Cynthia Ulloa

Will we have to memorize the Cv,m and Cp,m for the rotational motions? e.g. 3R for for nonlinear molecules

Cynthia Ulloa

Would it be a good idea to understand 100% the phase changes graph that was shown in class?

Cynthia Ulloa

Eruchi Okpara 2E wrote:How do you know which bonds need to be broken?

if you draw out the lewis structures you will be able to cross out any new bonds formed or any bonds that were broken. This method will make it easier to go about these problems involving bond enthalpies

Cynthia Ulloa

Hello y'all, I am still a bit confused as to what degeneracy is and why it is important for thermodynamics? can someone re-explain? thanks!

Cynthia Ulloa

Can someone briefly re-explain what would happen to our internal energy when our P is constant and the moles of a gas change versus when our P is constant and solids and liquids are involved? I more or less understand what the Professor said at Friday's lecture, but I just want clarification.

Cynthia Ulloa

When we compress a gas, are we adding heat?

Cynthia Ulloa

Would it be specified when to use Cv vs Cp or vice versa? Or how would we go about when to use one over the other?

Cynthia Ulloa

Hello, I was wondering if someone can explain to me why bond enthalpy is the least accurate?

Cynthia Ulloa

yes, the signs can definitely change when adding them up to get the total. As for the negative and positive signs, they let us know whether the reaction was endothermic, absorbing heat, or exothermic, releasing heat.

Cynthia Ulloa

Can someone re-explain how we would use bond enthalpies? Would we only account for the new formations?

Cynthia Ulloa

I think this is a topic we will be covering in 14B soon

Cynthia Ulloa

Hey y'all I am still having trouble understanding what buffer solutions are. Why is it that when we create our ICE tables we disregard the salts? How would we go about these types of problems?

Cynthia Ulloa

Would this be due to H2SO4 being a strong acid? so H3O+ would be the same value since it was completely dissolved

Cynthia Ulloa

does anyone know if the peer learning sessions will still take place tomorrow due to the holiday?

Cynthia Ulloa

Can someone explain why we wouldn't convert to molarity before solving the ICE table? I am confused as to why the solution manual didn't convert to molarity

Cynthia Ulloa

Kp is specific to the equilibrium constant for partial pressures of gases while Kc is used for molar concentrations such as when working with aqueous elements.

Cynthia Ulloa

Percentage protonation is a way for us to check if it was okay to approximate our concentrations rather than use the quadratic formula. So, if the percentage was less than 5%, then we are good to go, but if it is higher than 5%, we are going to have to go back and use the quadratic formula.

Cynthia Ulloa

Hi y'all I am having trouble understanding this problem. Can someone break it down for me and explain how to go about each one?

Cynthia Ulloa

Towards the end of the lecture today, the professor was talking about what would happen if the concentration was less than 10^-7. Can someone re-explain what he meant by this especially when he brought up using 10^-9?

Cynthia Ulloa

Samantha Kwock 1D wrote:If two reactions are added together to form another reaction, then their K constants are multiplied to give the new reaction's K constant.

can you explain why we would multiply the K constants when we add the reactions? Or is this just a property?

Cynthia Ulloa

In lecture today, Professor Lavelle gave us the reaction N2(g) + 3H2(g) --> 2NH3(g) and described what would happen if we increased N2, increased NH3, and decreased H2. Can someone please explain to me each scenario, I am a bit confused still.

Cynthia Ulloa

When K = 1, this means that the reaction has reached equilibrium. So, the amount of reactants and products would be the same.

Cynthia Ulloa

They are both a measure of pressure so you can use either one depending on what the question gives you. If they give you pressure in terms of atm then you would use atm or vice versa.

Cynthia Ulloa

From my understanding, if we increase the pressure of gases, the equilibrium constant will not be affected. The only way the equilibrium constant would be affected is if we changed the temperature.

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