CHEMISTRY COMMUNITY

lizzygaines1D

one of the rates must be the slowest rate.

lizzygaines1D

increase in temperature causes an increase in the rate constant (because you T2 is larger so Ea/R(1/T1 - 1/T2) is positive therefore lnK2/k1 is positive.

lizzygaines1D

it still requires energy to break ATP down, however you are gaining more energy from the release of P and your new bond is ADP which has less energy, so your net energy is a lot larger than what you supplied.

lizzygaines1D

its basically when the reactants sit on the surface of the catalyst.

lizzygaines1D

In a combustion reaction when you have a nitrogen in the reactant, how do you know which form of nitrogen (NO, NO2 etc) to put in the products to balance it out?

lizzygaines1D

I'm going to assume that if it was covered in class its fair game for the final.

lizzygaines1D

We do not have to know how to approach reaction mechanisms from a direct computational method right?

lizzygaines1D

Can someone clarify how to determine if you have an intermediate or not?

lizzygaines1D

For the example in lecture today:
NO+1/2O2---->NO2
NO2---->NO+O
O2+O----->O3
NO is not an intermediate because it is a catalyst. The only way we knew this is because the example was nitric oxide catalyses or is there any other ways to determine which molecule is the catalyst?

lizzygaines1D

Do catalysts speed up both the forward and reverse reaction?

lizzygaines1D

Hope this can clarify everything.

lizzygaines1D

For irreversible processes, potential is lost because the opposing pressure is less than maximum at each stage, but how does this correlate to work not being is maximal value?

lizzygaines1D

yeah just to add on and clarify because this problem was tricky and there was info given that you didn't need. the external pressure never changed throughout the reaction.

lizzygaines1D

If you are asked to find the average rate of the reaction of some period of time, (in this case time isn't needed to solve the problem) and no time units are given, what should the time units be? I thought it would be seconds, but in self test 15.2A in the book the rate was given in L^-1 x h^-1.

lizzygaines1D

Usually the question will give you the order, and if it doesn't it should give the units of k. If the units are inverse time units, you'll know its first order etc. etc.

lizzygaines1D

Okay this clarifies so much. thank you!

lizzygaines1D

An infinitesimal change is a change over a very very very short period of time, so short, that you can almost consider t as being 0. You'll see this in a reversible process.

lizzygaines1D

Okay I asked my TA and yes usually you should use the instantaneous unless told otherwise.

lizzygaines1D

Today in lecture for the reaction A+B--->C+D we assumed the reaction is an elementary second order reaction. Why can we assume this and when will you not be able to assume this?

lizzygaines1D

when going through reaction mechanisms, how can you determine which step is slower?

lizzygaines1D

How would you be able to differentiate between using the unique average rate and the unique instantaneous rate?

lizzygaines1D

In the text book under the half life formula for zero order reactions it says not used. What does that refer to?

lizzygaines1D

is w always 0 in a calorimeter?

lizzygaines1D

Does anyone know if and of the different R values, aka 3/2R or 5/2R will be given on the midterm?

lizzygaines1D

For the cell Cu(s)/Cu2+(aq)//M2+(aq)/M(s) how do you know that the Cu2+ is the anode and M2+ is the cathode?

lizzygaines1D

Calculate the standard Gibbs Free energy for I2(g)--->2I(g) when K=6.8 at 1200 K. So using deltaG=deltaGrxn+RTlnQ, I understand how to solve for everything else, but how would you find Q if you are not given a pressure or anything for the products and reactants?

lizzygaines1D

for 11.19 c "calculate the equilibrium constant at 25C for the decomposition of limestone: CaCo3(s)--->CaO(s)+CO2(g)" so using lnk=-deltaG/RT, for finding deltaG, would you use deltaGf for CaCo3 for calcite or aragonite? These values are so close it probably won't affect the answer, but fo...

lizzygaines1D

what's the difference is in finding the entropy of vaporization vs the standard entropy of vaporization?

lizzygaines1D

the question:
5.5 g of stainless steel is increased from 20 C to 100 C. what is the change in entropy? The specific heat capacity of stainless steel is .51 J/Cxg
Obviously you plug it into Cln(T2/T1), but then you have to multiply by grams? Why do you do this and when do you know when to do this?

lizzygaines1D

The change in entropy equations with constant temperature, or change in volume work for reversible and irreversible changes, but does the equation that accounts for a change in temperature also work for an irreversible change?

lizzygaines1D

8.15 b asks for when q = 0 which would always be true when no energy is transferred as heat. 8.16 b asks for when w = 0.

lizzygaines1D

For homework problem #19, you are asked how much heat is needed for a 500.0 g copper kettle with 400.0 g of water inside to raise the temp of the water form 22 degrees C to 100 degrees C. I understand using the q=mC x change in temp, but I'm assuming you have to account for the copper kettle absorbi...

lizzygaines1D

Why is the conjugate acid of O2- OH-? What happened to the second O?

lizzygaines1D

for the reaction 2HI + CaO---->CaI2 + H2O how can you tell that 2HI is the acid and CaO is the base?

lizzygaines1D

The book that while most times a double bond includes a sigma and pi bond, sometimes it will consist of a pi and pi bond. When does this happen and how are you supposed to know?

lizzygaines1D

For naming purposes, how can you tell which is the linking atom if it's not underlined?

lizzygaines1D

in the book it says acetic acid releases one hydrogen ion to water and any other Bronsted base present in the solution. Does that mean if there was more than one base it would donate more than one H, or will it only ever donate the last H?

lizzygaines1D

to further clarify, if you look at the example HCl+H2O--->H3O+Cl, HCl is your acid because it gives the H to H20 to form H30. H20 is your base because it receives the H from HCl.

lizzygaines1D

what was the biological function of cobalt? I missed that note in class.

lizzygaines1D

for the example in class [Co(NH3)5CL]ClH20 and the name was penta-ammine-chloro-cobalt(II)Chloride Dihydrate, what is the roman numeral (II) for?

lizzygaines1D

So for tetrahedral molecules, you'd place the lone pairs in between the each shared electron pair, but what about a trigonal molecule? I guess I'm confused as to the fact that you're supposed to place lone pairs on opposite ends, but in the book it will show to lone pairs next to each other when its...

lizzygaines1D

How can you tell when a molecule is going to be T-shaped vs. whether it will be trigonal pyramidal or planar? Do you have to draw them differently or you can somehow just tell with the formula?

lizzygaines1D

...is there a difference between a Lewis Acid/base vs. a regular acid/base? If so, what is it. Very confused.

lizzygaines1D

How do you know when you're supposed to draw a plain Lewis Structure, or the cool 3-D VSEPR one? Will the instructions tell you? Does it matter?

lizzygaines1D

yes to confirm this our group was told we wouldn't have to know the shape or draw it for this test.

lizzygaines1D

I'm pretty sure Test 3 will cover everything from chapter 1 not covered on the previous test (mainly Heisenberg) and all of chapter 2.

lizzygaines1D

basically you are spreading out the electrons until you can pair them all. Aufbau principle tells us that if you have more than one orbital in the subshell, you add a parallel spin to the different orbital. I like to think of it as spreading out the electrons before you pair them all up to get the l...

lizzygaines1D

Sometimes a question will ask you to find the longest possible wavelength, and sometimes you just have to find the wavelength. Either way you use the formula wavelength=CxH/work function. Is this right? If so what's the difference in finding the longest possible wavelength, or just the wavelength?

lizzygaines1D

if you were working with a different element, because of the difference in number of electrons, the Rydberg constant would be different.

lizzygaines1D

for Homework 1.33 a, the velocity of an electron is 3.6x10^3 km/s and the question asks for the wavelength of the ejected electron? How do you solve this when all you have is velocity?

lizzygaines1D

So when finding which reactant is limiting, the text suggest there are two ways to go about it: to use the stoichiometric ratio to find which is in excess, or to calculate how many moles of product each reactant can form. Do both of these methods apply for every problem, or will there ever be a time...

lizzygaines1D

yes to agree with my classmates, keeping a little value list is super helpful. I just list all the elements underneath the arrow and keep a small tally, crossing them out and updating them as I balance.

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