CHEMISTRY COMMUNITY

Adriana_4F

He said he made it easier for us by not making us upload pictures or using a scanner and he said to do the final honestly so I guess we won't need to show work?? I'm not 100% sure but that's what I think

Adriana_4F

extensive property: property that depends on the amount of matter.
Ex: mass, volume, length, charge

Intensive Property: Does not depend on the amount of matter
Ex: melting/boiling point, pressure, density, concentration

Adriana_4F

Believe in yourself everyone! We can do this! Take a deep breath for 3 seconds and exhale for 4. Think positively! A positive mind starts the grind! Also, superhero pose really works haha

Adriana_4F

This is a bit confusing, someone please clarify!

Adriana_4F

Q > K ----> Reactants are favored
Q < K -----> Products favored
Q = K -----> Equilibrium

Think about the concentration of reactants and products: When Q > K, the concentration (or activities) of products increase (numerator increases) causing the rxn to make more reactants

Adriana_4F

He said not to worry though, we have plenty of time. 3 hrs and 30 min for 6 questions!

Adriana_4F

No, it would weirdly affect the ph of the solution, especially when balancing it under acidic conditions.

Adriana_4F

Thank you for this.. it really helps! I also find "LEO" very useful---> "LEO" meaning Loss of Electrons

Adriana_4F

Professor Lavelle emailed us saying someone wrote: “I just finished the final. It took me 1 hr 12 minutes to complete, and I went very slowly and wrote out my work for each step taking plenty of time with each question, closed book."

!!!

Adriana_4F

S total= S(system) + S(surroundings)

Adriana_4F

Will the final still be worth 180 points now that it is take home and open book?? I really hope so :/

Adriana_4F

It's worth 180 points now.. I hope it won't be worth less now that it's open book :/

Adriana_4F

Is the final going to be worth the same amount of points??

Adriana_4F

ShastaB4C wrote:Is k’ and k prime have to be positive right? Like just because k’ is the reverse reaction doesn’t mean it has a negative sign

Yes, it always has to be positive because the Arrhenius Equation is always positive.

Adriana_4F

You should also know how to determine if it is a strong or weak acid! Strong acid--> greater Ka bc protons dissociate more. weak acid-->lower Ka

Adriana_4F

On the final make sure not to confuse k and K! K is the equilibrium constant and k is the rate constant.

Adriana_4F

Thank you so much! You helped us so much..we'll miss you!!!

Adriana_4F

Look out for Lyndon's study packets, they are very helpful and he usually has a big review session where he explains the answers. In my experience, they have helped a lot and are sometimes harder than the actual midterm/final, so they definitely prepare you well. When do you think he's going to pos...

Adriana_4F

Mai V 4L wrote:Hi oes anyone have a preferred online resource/chart they like to refer to for studying this topic? Like khan academy or a youtube video or something thanks!!

https://www.youtube.com/watch?v=zslB7dr-eZA

This video is very helpful!

Adriana_4F

ASetlur_1G wrote:
Manav Govil 1B wrote:Delta H can usually be written as q. This is derived from the equation $\Delta H = \Delta U + P\Delta V$ . $\Delta H = q + w -w = q$ , so $\Delta H = q$ .

But this is only for when pressure is constant right?

yes it is only when pressure is constant

Adriana_4F

You add a metal when there are no inert solids present in the reaction. Pt is commonly used and is an inert electrode in that it is a conducting agent

Adriana_4F

Since Fe had the lower cell potential it was being oxidized and Ag was being reduced.

Adriana_4F

Instantaneous rate decreases as time increases and becomes 0 when equilibrium is reached

Adriana_4F

Also just to add on, If the enthalpy is negative, the reaction is exothermic because heat is being released. If the enthalpy is positive, the reaction is endothermic because heat is being taken up by the rxn

Adriana_4F

There are no products being formed yet so the rate depends on the reactants.

Adriana_4F

I don't think they will deduct points unless you're using both types of K in the problem.Then they will get confused. A way that I remember is "Kc- c is for concentration" and "Kp p is for partial pressures". Same with deltGr- r is for reaction.

Adriana_4F

We need to know how each of the rate laws are derived. Here is a helpful picture

Adriana_4F

The slow step is the one that determines the rate law

Adriana_4F

deltaG=-nFEcell
if Ecell is positive, delta G will be negative meaning the reaction is spontaneous. If Ecell is negative, deltaG will be positive meaning the reaction will not be spontaneous

Adriana_4F

I think most of them will be given but the important ones we should remember are the rate laws for the different orders of reactions

Adriana_4F

What happens if the number of electrons transferred is different? Do you have to balance the equation to make it the same?

Adriana_4F

If a species loses electrons, it is oxidized. If it gains electrons it is reduced

Adriana_4F

Does anyone know if this will be on Test 2?

Adriana_4F

I thought it was the cathode's electron pulling potential since it is undergoing reduction. Is this wrong??

Adriana_4F

It makes sense to balance the H+ by adding OH- because we are in basic conditions. By leaving the H+ ions we are saying the solution is acidic

Adriana_4F

Here is an image that can help!

Adriana_4F

It is a solid electric conductor that allows electrons to flow to generate an electrical current. These are your anodes and cathodes. Oxidation takes place in the anode and the electrons are released through an external current to the cathode where reduction takes place.

Adriana_4F

It is to transfer electrons. A missing salt bridge will result in a more positive charge in the anode and a more negative charge in the cathode. In order to keep these charges neutral, the salt bridge allows electrons to travel from the anode to the cathode

Adriana_4F

Think of how an increase in the concentration of reactants will increase the formation of products
The same will happen for Ecell. Ecell will increase

Adriana_4F

Hussain Chharawalla 1G wrote:However, as mentioned in lecture, remember that platinum one one side of the cathode or anode does not imply it is being used on both ends.

How do you know when you need to put it on both ends?

Adriana_4F

This is the same Question as 6M.1 in 7th edition but worded differently. It does not have the part about Cu being connected as the anode so I cannot assume that in 6M.1. Was there just a mistake in the solutions manual??

Adriana_4F

I got 1.04 V but the solution is -0.349 and I do not know why. Here's my attempted answer: Oxidation (Anode): M-->M^+ + e^- Reduction (Cathode): Cu2+ +2e- ------> Cu Ecell= E(cathode)-E(Anode)= -0.689V -0.689V= 0.34V- E(Anode) E(Anode)=1.04V If anyone knows why this is wrong can you say why?? Thank ...

Adriana_4F

Since the copper is being reduced doesn't it shouldn't 0.34 be the cathode potential?

Adriana_4F

As you can tell by the graphs, The reversible path does more work than the irreversible path. The reversible path generates the maximum amount of work a system can do.

Adriana_4F

Cv=3R/2
Cp=5/2R

5/2R=3R/2+R
5R-3R/2 --> 2R/2=R

Adriana_4F

To add on, the relationship between C v and C p is C p = C v + 1. The values for C v are shown below (know that we look at the ideal gas values): https://azchemistry.com/wp-content/uploads/2018/03/Examples-of-Monatomic-and-Diatomic-Gases.png It's not one it is actually R, the gas constant. Cp=Cv + R

Adriana_4F

The definition of Enthalpy (deltaH) is the amount of heat released or absorbed at a constant pressure, so qp and deltaH can be used interchangeably.

Adriana_4F

Matt Sanruk 2H wrote:And this would be irreversible?

Yes this would be irreversible

Adriana_4F

An isothermal expansion One of the characteristics of an ideal gas is that there is no interaction between gas molecules. This means the molecules will not have any potential energy so the only contributor to the change in internal energy would be its kinetic energy due to its absolute temperature. ...

Adriana_4F

They changed the units from kJ to J
1.0x10^4 kJ = 1.0x10^7 J

Adriana_4F

For an ideal gas, Cp,m=Cv,m + R
Cp,m is the molar heat capacity at a constant pressure
Cv,m is the molar heat capacity at a constant volume
R is the gas constant

Adriana_4F

An irreversible process happens when a constant external pressure is acting on (let's say) a gas. Imagine attaching a heavy weight to a spring; the spring will stretch, however, once you take off all the weight the spring will not be able to revert back to its original size. This is an irreversible ...

Adriana_4F

The heat lost by the reaction is equal to the heat gained by the calorimeter (qcal=-qrxn). In order to calculate the change in internal energy of the reaction, you need to know the amount of heat that was lost by the reaction, so you do the opposite of that equation (qrxn=-qcal => qrxn=-Ccal(delta T))

Adriana_4F

One of the characteristics of an ideal gas is that there is no interaction between gas molecules. This means the molecules will not have any potential energy so the only contributor to the change in internal energy would be its kinetic energy due to its absolute temperature. Since it is isothermal, ...

Adriana_4F

Electron Affinity is the energy change when a neutral atom attracts an electron to become a negative ion. So yes you are, in a way, correct

Adriana_4F

Yes, it would not be covalent anymore it would be ionic. The guidelines are: If the electronegativity difference is greater than 2 then it is an ionic bond. If the electronegativity difference is less than 1.5 then it would be a covalent bond. If the difference is between 1.5 and 2 then it would be ...

Adriana_4F

Tetrahedrals are 3D shapes, not 2D. If they were 2D shapes then the angles would be 90 degrees. Remember that the shapes of molecules should be in 3D since we live in a 3D world

Adriana_4F

He has not told us what will be on the test yet but I'm guessing it's going to be on everything we learned after the midterm

Adriana_4F

What do you do to a dead chemist?

You barium

Adriana_4F

Remember that in the equation E=hv, E is the energy of only one photon...in this case photons are equivalent to particles so you would have to find out how many particles are in 5 mol of the substance and multiply that by the answer you got....that way you calculated the amount of energy ejected by ...

Adriana_4F

Stemming from what the person above said, hydrogen bonds are intermolecular not intramolecar...They are also make the strongest bonds

Adriana_4F

Covalent bonds are for intramolecular bonds while hydrogen bonds are for intermolecular bonds. in simpler terms, a covalent bond is what actually glues the H2 and O atoms to make a molecule while the hydrogen bond glues the H2O molecule with other H2O molecules to make water.

Adriana_4F

The type of atom does not affect the shape, the number of atoms do. Remember that the shape has to be a 3D shape not 2D because we live in a 3D world. Hope this helps :)

Adriana_4F

Stemming from what the last post said, if you were to melt ice, it is still H2O so the intramolecular molecules are not affected. The state of the H20 is affected though...that shows a change in intermolecular forces.

Adriana_4F

Here's a video on the basics of Lewis structures: https://www.youtube.com/watch?v=1ZlnzyHahvo
I hope this helps :)

Adriana_4F

I think the reason why is because the periodic table was created before orbitals were even discovered. The periodic table is organized in such a way that elements are grouped with other elements because of how similar in reactivity they are (ex: alkaline metals, noble gases, etc.). If you need more ...

Adriana_4F

Are you talking about Lewis structures? If so here's a video: https://www.youtube.com/watch?v=1ZlnzyHahvo
I hope this helps :)

Adriana_4F

Do we at least have to know what it's about? Or will the test just be all math?

Adriana_4F

What do you mean by resting mass?

Adriana_4F

https://www.youtube.com/watch?v=Tilkl4lRqzo

Adriana_4F

Is this going to be similar to the test next week?? Also what specific concepts do we not need to know other than Schrodinger's equation?

Adriana_4F

I was just wondering how did you prepare/study for the MCAT and get into medical school in general? I'm very interested in hearing your journey! But overall thank you so much for the, it was extremely helpful :)

Adriana_4F

I took chemistry in sophomore year of high school, but it was mainly a worksheet type class more based on completion than anything else, so I'm pretty rusty as well. I've attended the Peer Learning Facilities with the UAs though and that really seems to help as you can ask any questions you want an...

Adriana_4F

I also have a question: when you have a reaction in the form of MgSO4.7H2O where the 7 is in front of the H2O, would you have to do 7x(molar mass of H2) + the molar mass of O or 7x(the molar mass of H20)?

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