CHEMISTRY COMMUNITY

Samantha Chang 2K

Lavelle said we can pick up our final exam in 3034 Young Hall Week 3 of Spring Quarter!

Samantha Chang 2K

Yes, and remember that an irreversible reaction will always require less work.

Samantha Chang 2K

Yes, they are correlated for Gibbs Free energy

Samantha Chang 2K

I am guessing the new material will be heavily weighted, but you cannot really predict with Lavelle's tests. It is safe to say that everything is fair game...

Samantha Chang 2K

Indeed Nathan Tran.

Samantha Chang 2K

The unique rate is a rate of a reaction divided by its stoichiometric coefficient. A unique rate will be the same for each reactant or product but the product will be a negative value.

Samantha Chang 2K

Very intriguing questing Nathan Tran. I am glad you asked this to further facilitate the conversation of Kinematics.

Samantha Chang 2K

Water can be solid, liquid, or gas.

Samantha Chang 2K

Information about review sessions was sent in a new email :)

Samantha Chang 2K

Ecell=Ecathode-Eanode

Samantha Chang 2K

Half life reactions are just 1st order reactions!

Samantha Chang 2K

Free energy is a state function!

Samantha Chang 2K

If Gibbs Free Energy is negative, it is spontaneous.

Samantha Chang 2K

The reaction will eventually stop when there are no more ions trading off.

Samantha Chang 2K

For redox reactions you have to do both, balance, like we learned in high school, and make sure the charges are even.

Samantha Chang 2K

The anode and the cathode are deemed right and left just as a formality so you can tell where the reactions are taking place. An anode is the oxidation part of the reaction and the cathode contains the reduction part of the reaction.

Samantha Chang 2K

Yes, when delta G is negative it is spontaneous and when delta G is positive it is not spontaneous. When delta. G is 0, it is at equilibrium.

Samantha Chang 2K

When do we use this equation to find internal energy? And where does the 3/2 come from for this equation?

Samantha Chang 2K

In a closed system, heat can still travel in and out of it, but in an isolated system nothing can affect the internal energy(that is why U=0 for a closed system).

Samantha Chang 2K

W=-PdeltaV is utilized when pressure IS constant which was shown in lecture through a definite integral because we could factor out the constant of pressure and we are left with the integral dv which just means V2-V1 if we put it into a definite integral. We use the other equation -nRTln(V2/V1) when...

Samantha Chang 2K

In lecture Lavelle defined degeneracy as the number of ways of achieving a given energy state, and it can help us find entropy.

Samantha Chang 2K

Thanks Joyce!

Samantha Chang 2K

I am terrible at explaining, but here is the video I watched: https://www.youtube.com/watch?v=54n1XppP-lA and I got confused with the example at 25:46 when the initial concentrations of the products were not 0.

Samantha Chang 2K

Condensations is an exothermic process!

Samantha Chang 2K

If there are the same number of moles on both sides of the equation and you increase/decrease the volume then does the equation shift to the left or right?

Samantha Chang 2K

I was watching a YouTube video, and I got a bit confused on a topic. If you are given initial concentrations and the Kc value, and the Qinitial>Kc then do you switch the x signs for change in molarity when doing the ICE table to find the final equilibrium concentrations? If so, then why?

Samantha Chang 2K

Thank you!

Samantha Chang 2K

Solving for Q is the same as solving for K. When Q is less than K, forward reaction is favored. When Q is greater than K, reverse reaction is favored.

Samantha Chang 2K

We can know if a reaction is endothermic when heat is absorb and in contrast an exothermic reaction is when heat is released. This is how one can environmentally tell if a reaction is exothermic and endothermic. Other than that, I think one has to know if delta H is negative or positive.

Samantha Chang 2K

What does it mean when "expansion occurs" on a certain reaction?

Samantha Chang 2K

pH can be negative, but in class it the pH utilized will mostly be in the range of 0-14. pH can be negative with super acids!

Samantha Chang 2K

A liquid cannot be aqueous, but it can be a solid, liquid, and gas.

Samantha Chang 2K

When using the ICE box, you can use partial pressure and molarities/concentrations.

Samantha Chang 2K

On an email given Lavelle said homework can be either equilibrium, or acids and bases, or some of both as it is all ‘recently covered material’.

Samantha Chang 2K

When converting to Kp and Kc, you use the ideal gas law, P=concRT, and you use the concentrations given to find pressure in atm.

Samantha Chang 2K

Kc is specifically the molar concentration [P]/[R], and K is just an overall equilibrium constant.

Samantha Chang 2K

Homework questions are 7 points a week (70 points per quarter) and the 3 chemistry community posts are 3 points a week (30 points per quarter).

Samantha Chang 2K

Yes, you are correct, solids do not have concentration, and neither do pure liquids; therefore, they cannot be used to calculate for K.

Samantha Chang 2K

Are we going to be tested on naming coordination compounds? There was a little bit of confusion in my UA session because the UA said that Lavelle was supposed to remove naming from the curriculum.

Samantha Chang 2K

Yes, a lone pair is considered a region of electron density and therefore you will count it to find hybridization.

Samantha Chang 2K

Thank you!

Samantha Chang 2K

Can someone elaborate what polar power is? And why a high charge and a low volume affect it?

Samantha Chang 2K

A stands for the central atom!

Samantha Chang 2K

Samantha Chang 2K

Samantha Chang 2K

Yes! Everything that was not covered on the midterm!

Samantha Chang 2K

Thank you Dr. Lavelle!

Samantha Chang 2K

The center atom would be oxygen because if you look at the periodic table it has the lowest ionization energy.

Samantha Chang 2K

The center atom would be oxygen because if you look at the periodic table it has the lowest ionization energy.

Samantha Chang 2K

Having a 0 formal charge is most important, unless it is an ion; therefore the formal charge has to be equal to the charge of the ion. Sometimes lewis dot structures can have expanded octet.

Samantha Chang 2K

Dr. Lavelle said it depends on if we are behind or ahead.

Samantha Chang 2K

Could someone explain 13c to me? -13c is a Heisenberg Uncertainty Principle problem. The equation for this problem is ΔPΔX=>h/4pi. For this equation we need the mass, the velocity(these two values multipled together are ΔP), and we need ultimately to find ΔX. -We are given the mass which is 2.8 gra...

Samantha Chang 2K

3b) in the second experiment if the same threshold voltage is applied to the mercury lamp(that is now significantly contaminated by atoms with a higher threshold energy) what will happen to the intensity of the light emitted? Will the intensity not be affected? I have a hard time conceptually graspi...

Samantha Chang 2K

3b) in the second experiment if the same threshold voltage is applied to the mercury lamp(that is now significantly contaminated by atoms with a higher threshold energy) what will happen to the intensity of the light emitted? Will the intensity not be affected? I have a hard time conceptually graspi...

Samantha Chang 2K

The degeneracy of a 4p orbital will be 3 because they all have the same energy level.

Samantha Chang 2K

The mass composition percentage has to add up to 100%.

Samantha Chang 2K

Thanks guys! This really helped :)

Samantha Chang 2K

Samantha Chang 2K

Why do we choose the atom with the lowest ionization energy as the central atom for Lewis Dot Structures?

Samantha Chang 2K

The change in energy can be negative(exothermic) or positive(endothermic). In this case the change of energy is exothermic in which energy is released, so the value will be negative.

Samantha Chang 2K

1eV= 1.6022 x 10^-19Joules

Samantha Chang 2K

Yes, a nodal plane is in a region of zero electron probability meaning the planes are perpendicular to the internuclear axis. For example, the S orbital has no internuclear axis; therefore, it has no nodal planes.

Samantha Chang 2K

I would round the answers to the significant figures towards the end because it would provide the most accurate answer. Throughout the problem I would use the most amount of decimal places in order to obtain a precise number until the end.

Samantha Chang 2K

Amplitude measures the height of each wave and equates to the energy or intensity of the light. The amplitude does not have any effect on the frequency. Wavelength and frequency are inverses of one another, so if one increases the other one decreases. This is based off of the equation c(speed of lig...

Samantha Chang 2K

Thank you so much Karen! I was looking for more practice problems <3

Samantha Chang 2K

For this upcoming test, I would memorize the formulas needed, for there are not that many. We will get a periodic table for the molecular masses though.

Samantha Chang 2K

1. Convert 1Kg H2O to grams
2. Convert the grams of H2O to moles using molar mass of H2O (you can add masses up using the periodic table)
3. Convert the moles to molecules using Avogadro constant (6.022*10^23)
:)

Samantha Chang 2K

Usually the problem indicates what units should be utilized for the answer. If not, stick to your standard metric units of measurement, such as liters, grams, and meters. These are additionally the units employed in most chemistry concepts like molarity and quantum chemistry.

Samantha Chang 2K

Empirical formula represents the relative number of atoms in a molecule, so I would just round up to the nearest whole number if it is that close. I would say that 8.94 and 10.92 are close enough to be rounded up. In the problems that we are given, it is usually apparent whether we need to multiply ...

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