CHEMISTRY COMMUNITY

Alfred Barrion 2H

For simplicity, it would be easier to use Kelvin, especially since Kelvin is used in the constants.

Alfred Barrion 2H

No need to print out anything for the final! If you feel more comfortable with the constants and equations sheet printed out, maybe that will be helpful.

Alfred Barrion 2H

k can only change when there is a temperature change.

Alfred Barrion 2H · Re: Final Exam Time The final will be 3 hours and 30 mins! From 11:15AM-2:45PM

The final will be 3 hours and 30 mins! From 11:15AM-2:45PM

Alfred Barrion 2H

I feel like some questions on the final would be structured similarly to hw questions.

Alfred Barrion 2H

I believe it was used to show how the equations work but would not necessarily be applied on a test.

Alfred Barrion 2H

In Lavelle's email he said it would be a quiz posted on CCLE.

Alfred Barrion 2H

I would make sure you have a broad understanding of Lavelle's course outlines, but to also be mindful of kinetics since it is our most recent material!

Alfred Barrion 2H

I'll be taking 14BL this summer as well, does anyone have any experience?

Alfred Barrion 2H

I think its really similar to Chem 14A, 50% is a C-, and he will scale depending on class performance, but it will not hurt you.

Alfred Barrion 2H

Per his last email, Lavelle said that he didnt want us to go through the trouble of scanning or using different apps. I think it will just be some multiple choice and fill in the blank questions.

Alfred Barrion 2H

Yes, the coefficients in a chemical equation affect the K constant.

Alfred Barrion 2H

It honestly depends on the context of the question, but I use seconds because it is the SI unit. It also depends on your k.

Alfred Barrion 2H

Yes, because at a higher temperature molecules move faster and have more collisions.

Alfred Barrion 2H

Delta U is change in internal energy while delta H is a change in enthalpy.

Alfred Barrion 2H

His last email said that he would be telling us by tomorrow the format of the final. All I know is that its open book and online.

Alfred Barrion 2H

I think the take home final will be in the same time period as the regular final.

Alfred Barrion 2H

Intensive properties are not affected by changes in matter. Extensive properties change when the amount of matter changes.

Alfred Barrion 2H

Dr. Lavelle, Thank you so much for exposing me to the world of chemistry in my short first year at UCLA. I am so grateful for the way you taught chemistry and worked so hard to coordinate office hours, step-up sessions, and workshops. To all of the TAs and UAs reading this. Thank you from the bottom...

Alfred Barrion 2H

The final should be up around Sunday! Lavelle has been finalizing things so be sure to check his emails.

Alfred Barrion 2H

We can use our books in pdf or physically, as well as any notes we have prepared.

Alfred Barrion 2H

I think they will be posted in the same thread where the worksheet was posted.

Alfred Barrion 2H

The comma is for something in the same phase, such as two aqueous. The | is used to separate substances in different phases.

Alfred Barrion 2H

I would ask your TA for more information to pick up Test 2

Alfred Barrion 2H

Catalysts help speed up reactions though.

Alfred Barrion 2H

Salt bridges help with electron flow and neutralizing the solutions in a galvanic cell.

Alfred Barrion 2H

In the email he said that the final will be shorter and open book. My TA said that it would be collected online.

Alfred Barrion 2H

We wouldn't necessarily use the derivations on the exam, but knowing how the derivation occurs and how it leads to a specific equation would be valuable in decoding a certain question.

Alfred Barrion 2H

They are typically provided on the list of given equations!

Alfred Barrion 2H

I feel like we would have to print the final out and scan it, I'm waiting for an update as well!

Alfred Barrion 2H

Lavelle's email said you can send a picture to your TA.

Alfred Barrion 2H

I think that Lavelle is in control of what goes on the final.

Alfred Barrion 2H

You should use Kelvin since it matches with the gas constant R to cancel out.

Alfred Barrion 2H

A first order reaction depends on the concentration of one of the reactants. A second order reaction is the square of the concentration of a single reactant.

Alfred Barrion 2H

When Ecell > 0, then K>1.
When Ecell < 0, then K<1

Alfred Barrion 2H

The graph of [A] v. Time would be linear.

Alfred Barrion 2H

An intermediate is formed and then used up during a reaction, so it cant be used in rate law.

Alfred Barrion 2H

You should use a positive sign, especially when regarding voltage because it can determine if a charge is positive or negative.

Alfred Barrion 2H

Only the second part of thermodynamics and electrochemistry is covered in test 2.

Alfred Barrion 2H

Kinetics is used to tell the rate of a reaction, instead you can use thermodynamics to determine if a rxn is favorable.

Alfred Barrion 2H

Typically the unit for rates is mol per liter per time unit.

Alfred Barrion 2H

I'm pretty sure that test 2 covers all of electrochemistry and the second page of the thermodynamics outline (not covered in the midterm)

Alfred Barrion 2H

the lower the pKa = the stronger the acid

Alfred Barrion 2H

you use -x typically for the reactants and +x for the products

Alfred Barrion 2H

k is used when at equilibrium and q is used when not in equilibrium

Alfred Barrion 2H

We dont include units for Kp because its a constant.

Alfred Barrion 2H

How does Q let us predict the direction that an equilibrium practice will go through?

Alfred Barrion 2H

Hi, I really don't get how to differentiate between Kc and Kp.

Alfred Barrion 2H

R is the gas constant, and depending on the units you have in your problem you have to choose a certain R value.
R = 8.314 J·K-1·mol-1 = 8.206 x 10-2 L·atm·K-1·mol-1 = 8.314 x 10-2 L·bar·K-1·mol-1
= 62.364 L·Torr·K-1·mol-1

Alfred Barrion 2H

Most likely outline 1 and some of outline 2, whatever he covers right before the test is on the test I think.

Alfred Barrion 2H

We went over porphyrin ligands and the effects in hemoglobin in lecture so I think its fair game for the final.

Alfred Barrion 2H

Well more H3O+ in the blood would lower pH not make it higher.

Alfred Barrion 2H

You use ferrate and cuprate when naming a coordination compound.

Alfred Barrion 2H

Dr Lavelle said you can use IUPAC or the regular naming as long as you stay consistent with it.

Alfred Barrion 2H

q1 and q2 stand for the charges on the interacting objects.

Alfred Barrion 2H

I really like using adobe spark for flashcards, its really customizable.

Alfred Barrion 2H

I dont think we need to know equilibrium that deep, but we did talk about k constants in lecture. We're only expected to do calculations on weak acids/bases though.

Alfred Barrion 2H

Whats the difference between cisplatin and transplatin?

Alfred Barrion 2H

Cisplatin can be used in chemotherapy treatment by stopping cell division but I'm not quite sure if it's naturally occurring...

Alfred Barrion 2H

For the final, try going to as much review sessions as possible that are focused on topics that you need the most help on. I recommend looking for some of the worksheets that the UAs make they're really helpful!

Alfred Barrion 2H

Bond length is a component of relative acidity. Since the bond length in HI is longer and weaker compared to the short and strong bond in HF, HI is able to dissociate much easier in a solution compared to HF.

Alfred Barrion 2H

The pH equation is on a logarithmic scale and is -log[H⁺]
You basically find the negative log of the concentration of H⁺ in a solution to find the pH in a strong acid.

Alfred Barrion 2H

Hi can someone tell me how Lewis and Bronsted acids are different or similar?

Alfred Barrion 2H

I feel like you should go to the review sessions for topic that you need the most help in. Also office hours too!!

Alfred Barrion 2H

I think we'll be going over ICE tables in 14B. Lavelle said we should know how to calculate pH for strong acids and bases, but i think we just need to know K value for weak acids and bases.

Alfred Barrion 2H

EDTA can remove metals from a solution. So if your blood had elevated levels of a deadly metal such as mercury, EDTA can help remove it from your bloodstream.

Alfred Barrion 2H

The molecular shape of carbon dioxide is linear bc there's no lone pairs and it has 2 domains.

Alfred Barrion 2H

the electron pair geometry for NCl2 is tetrahedral since there are 4 domains.
the molecular geometry is bent

Alfred Barrion 2H

You have to count the atoms around the atom you're looking at in a molecule.
If there are 4 atoms around the central atom, you'd have sp³
If there are 3 atoms around the central atom, youd have sp²
If there are 2 atoms around the central atom, youd have sp¹

Alfred Barrion 2H

Usually a sigma bond occurs in single bonds, double bonds and triple bonds.
pi bonds are found in double and triple bond.
Each bond type has a sigma bond
Ex. Double bond=one sigma, one pi
Triple bond: one sigma, two pi

Alfred Barrion 2H

Yes, hydrogen bonding should have a partial positive or negative charge.

Alfred Barrion 2H

I don't think you need to know pentagonal bipyramid because its not THAT common, but its nice to know more VSEPR shapes!

Alfred Barrion 2H

In a square pyramidal all angles are <90 degrees
In a t-shape the angles are <90 degrees

Alfred Barrion 2H

Depending on the IMFs that the molecules have you can compare them to determine which molecule has a higher boiling or melting point.

Alfred Barrion 2H

isn't CBrCl2 tetrahedral so its polar??

Alfred Barrion 2H

Both have the same trend on the periodic table, but what is the difference between the two?

Alfred Barrion 2H

The magnetic quantum number, m_l tells you the number of orbitals and the way its oriented in a sub shell. it ranges from -l to l.

Alfred Barrion 2H

Why is it when there is a resonance structure, all of the bond lengths are the same even though there's double and single bonds.

Alfred Barrion 2H

You would want the formal charge on the central atom to be closer to zero because its supposed to be the least electronegative.

Alfred Barrion 2H

I would focus on lewis structures and resonance because it plays a huge role in drawing a stable structure!

Alfred Barrion 2H

Why do certain elements make anions and others make cations?

Alfred Barrion 2H

Why are double bond lengths shorter than single bond lengths?

Alfred Barrion 2H

Why is Fluorine touted as the most electronegative atom? What makes it so electronegative?

Alfred Barrion 2H

Why do shared atoms want to be at a noble gas configuration?

Alfred Barrion 2H

Why exactly can P, S, and Cl have more than 8 valence electrons?

Alfred Barrion 2H

As you remove more electrons from an atom, the attraction between electrons and the nucleus increase because repulsion decreases. So as you go through successive ionization energies, more energy is required to remove electrons due to the lack of repulsion.

Alfred Barrion 2H

Why does Cr and Cu not follow the rules for electron configuration? Why isn't the s block completely filled?

Alfred Barrion 2H

We draw arrows going up first because each electron must enter an empty orbital first before going into the same orbital because of repulsion (two electrons repel). By putting the arrows up before down, it shows how we can minimize repulsion in a specific element.

Alfred Barrion 2H

In some answers, the orders may be reversed due to some exceptions in the Aufbau principle in elements such as Cr and Cu.

Alfred Barrion 2H

For ounce to grams use 1 ounce = 28.3 g
For mph to m/s use 1 mph = 0.447 m/s

Alfred Barrion 2H

The change in energy was negative because we went from a high to low energy level (n=4 to n=2). When finding the frequency, we made the energy positive because you can't have a negative value of Hertz as your answer, since a wave's frequency can not be -6.17*10^14 per second.

Alfred Barrion 2H

Spectroscopic analysis is the analysis of light emitted by a certain substance. We can use a device called a spectrometer to analyze light (it involves the use of a prism to separate different wavelengths of light). This gives us spectral lines that allow us to analyze light further.

Alfred Barrion 2H

The Balmer series is found in the visible region of the hydrogen spectral lines and goes from n=3,4,5,... to n=1
The Lyman series is found in the ultraviolet series of the hydrogen spectra and goes from n=2,3,4,... to n=2

Alfred Barrion 2H

The diameter of an electron is approximately < 10−18 m.

Alfred Barrion 2H

When a wavelength is shorter, its frequency is higher therefore there is more energy. Using the equation E=hc/lambda (lambda is the wavelength), a shorter wavelength would make energy hbiggergher, and a longer wavelength would make energy smaller.

Alfred Barrion 2H

Problems usually require us to use the least amount of sig figs from the "given" in the problem. Say you get a problem that gives you the following info: 0.179 M AgNO3 and 0.50 L. You would only round your answer to the least amount of sig figs given in the problem, this being 2 sig figs f...

Alfred Barrion 2H

Dilution problems typically use the term "stock solution" when one wants to dilute a certain compound. For example a problem might say you have a stock solution of 12.0 M NaOH and it would want you to figure out how much stock solution is needed to get 250. mL of 2.0 M NaOH. The word "...

Alfred Barrion 2H

For more accuracy, you should use all decimal places on the periodic table that is provided. Feel free to round to the amount of sig figs needed at the end of the problem.

Alfred Barrion 2H

You can usually tell if something is solid or gas by looking through the problem you are doing (it is normally given) and it is usually marked on the periodic table. You can determine if a solution is aqueous if you see that it is being dissolved in water or if ions/precipitates are involved in a pr...

Alfred Barrion 2H

Hi all, It's been a long time since I've taken chem, but I was wondering if you need to keep on using sig figs on the intermediate steps of a problem. Say your answer has to be 3 sig figs, do I have to keep on using 3 sig figs for each step in the middle of the problem or implement it in the end? Th...

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