CHEMISTRY COMMUNITY

Sean Wang 1F

If Q is less than K, then products are favored because the numerator needs to increase. If Q is greater than K, then reactants are favored because the denominator needs to increase.

Sean Wang 1F

Yes that's correct, Kfwd/Krev is equal to K.

Sean Wang 1F

N is the amount of electrons transferred in the redox reaction. Make sure to scale the equations so that the electrons transferred in both half reactions are the same.

Sean Wang 1F

Activation energy is the energy needed to start a reaction and free energy of activation is gibbs free energy.

Sean Wang 1F

I'm planning on relaxing over the summer and taking Physics 5A.

Sean Wang 1F

0.693 comes from ln(2).

Sean Wang 1F

For cell diagrams, don't include the coefficients, just the phases.

Sean Wang 1F

For zero and first order reactions, the slope is -k. For second order reactions, the slope is +k.

Sean Wang 1F

A zero order reaction means that the concentrations of the reactants do not dictate the rate of the reaction. A first order reaction means that the rate of the reaction is dependent on the concentration of one of the reactants. A second order reaction means that the rate of the reaction is dependent...

Sean Wang 1F

Like others have said, we aren't expected to find the intermediate species. However, I think that he may give us a problem where he tells us what the intermediate species is and we have to apply that.

Sean Wang 1F

In this equation, n is the number of moles of electrons transferred in the redox reaction.

Sean Wang 1F

Yes, for sapling, you should include states of matter unless it says that they are optional.

Sean Wang 1F

Yes, the oxidizing agent is the molecule being reduced and the reducing agent is the molecule being oxidized.

Sean Wang 1F

The anode is where oxidation occurs and the cathode is where reduction occurs.

Sean Wang 1F

The phases are normally the same as the one given in the problem. Ions are aqueous and water is liquid.

Sean Wang 1F

To convert between Cv and Cp, you can use the formula Cp = Cv + R.

Sean Wang 1F

Open systems allow both matter and energy to exchange with surroundings. Closed systems allow only energy to exchange with surroundings. Isolated systems allow neither matter nor energy to exchange with surroundings.

Sean Wang 1F

Q is calculated the same way as K, just Q is the constant when not at equilibrium.

Sean Wang 1F

E is not a state function because it depends on the path taken, you can't just look at the final and initial value.

Sean Wang 1F

The 2nd law of thermodynamics says that when a spontaneous change occurs, the entropy will increase.

Sean Wang 1F

A closed system is where only energy can exchange with the surroundings and matter cannot, whereas in isolated systems neither matter nor energy can exchange with the surroundings. An example of a closed system is a closed beaker, while an example of an isolated system is a closed beaker surrounded ...

Sean Wang 1F

It isn't necessary to memorize the values because they are provided in the equation sheet.

Sean Wang 1F

K=1 is extremely rare because it means that the concentrations of the products and reactants are exactly equal at equilibrium. This means that neither the product or reactant side is favored.

Sean Wang 1F

Yes, like dH both dG and dS can be added/subtracted/multiplied by a coefficient because they are all state functions.

Sean Wang 1F

I believe J/K is the standard unit and the most common, however they can always ask for kJ/K so I would always double check the units they ask for.

Sean Wang 1F

It depends on the system, phase changes can occur at both constant temperatures and constant pressures.

Sean Wang 1F

S will equal 0 when the system is an isothermal reversible reaction.

Sean Wang 1F

Entropy is the amount of disorder in a system.

Sean Wang 1F

Yes, the equation Cp=Cv+R can be used to convert between Cp and Cv.

Sean Wang 1F

I believe that they are mostly with hydrocarbons, but they do not have to be. An example would be the combustion of hydrogen gas. 2H2(g)+O2(g)→2H2O(g)

Sean Wang 1F

To convert from pKa to Ka use Ka=10^-pKa.

Sean Wang 1F

Another way of thinking about it is that the conversion from celcius to kelvin is just addition. There isn't any multiplication or division which means that a change in 1 degree of kelvin is the same as a change in 1 degree of celcius.

Sean Wang 1F

Last quarter in 14A, grades normally took about a week to be released on CCLE.

Sean Wang 1F

At the same temperature, steam causes a more severe burn than water because steam contains more heat and energy because it requires heat to change liquid to vapor.

Sean Wang 1F

Inert gasses do not affect equilibrium partial pressures because they are non-reactive and therefore not affecting the volume.

Sean Wang 1F

A is just a placeholder because the actual weak acid isn't specified. If a weak base isn't specified, it would be B + H2O yields OH- + HB+.

Sean Wang 1F

When there is an initial concentration, use -x. When the initial concentration is 0, use +x.

Sean Wang 1F

We can approximate that x is near 0 when the K value is less than 10^-4.

Sean Wang 1F

Yeah, I would focus on the problems he specified as I think the rest of outline 3 will be on the next midterm.

Sean Wang 1F

From outline 3, it says we should do 4D: 1, 3,5, 7, 9, 11, 15, 17, 19, 21, 23

Sean Wang 1F

For this question use the 1st and 3rd equation. You use these two because you can combine them to make the equation in the example. First, multiply the first equation by 3. When you multiply the equation by a value, you have to bring the K value to the power of the coefficient. So, your new K value ...

Sean Wang 1F

It depends on the units of pressure that are given. We should use 8.206 x 10^-2 when given atms or bars because 1 atm is approximately 1 bar.

Sean Wang 1F

The equation shifting to the right means that the reaction is more inclined to form products. The equation shifting to the left means that the reaction is more inclined to form reactants.

Sean Wang 1F

I would assume that we would need to memorize them because in 14A we were expected to memorize them.

Sean Wang 1F

Why does adding heat to an exothermic reaction favor the formation of reactants?

Sean Wang 1F

Kc is used for concetrations while Kp is used for partial pressurse.

Sean Wang 1F

I don't believe they carry over. I would just do 5 posts every week.

Sean Wang 1F

Yes, Q is the reaction quotinent. Use Q when the reaction is not at equilibrium and use K when the reaction is at equilibrium.

Sean Wang 1F

You shouldn't have to play catchup. Just do 5 posts every week and you should be fine.

Sean Wang 1F

Like Varsha said, the value of R depends on the units given. If you're in doubt I believe that in this class, we are most commonly given atms which mean you use 8.206 x 10^-2 for R.

Sean Wang 1F

Since water is amphoteric, it can act as both an acid or base

Sean Wang 1F

Acid rain is caused by pollutants releasing CO2, SO2, and NO2, which interact with h2o to form acids.

Sean Wang 1F

A bigger Ka value corresponds to a greater strength of an acid, while a bigger pka value corresponds to a weaker strength of an acid.

Sean Wang 1F

Sigma bonds consist of hybrid orbitals, pi bonds consist of unhybridized orbitals. If there was another pi bond it would also be (C 2p, O 2p).

Sean Wang 1F

Why is it important that pi bonds cannot rotate, while sigma bonds can? What types of problems do we apply this to and how?

Sean Wang 1F

Yes, these are the same things.

Sean Wang 1F

Here's the link to a page I found on Professor Lavelle's website. I think we should be expected to know all of these.
https://lavelle.chem.ucla.edu/wp-content/supporting-files/Chem14A/NamingCoordinationCompounds.pdf

Sean Wang 1F

I'm pretty sure in the lecture Professor Lavelle said that we should just narrow it down to tetrahedral/square planar and wouldn't be expected to know which one it is.

Sean Wang 1F

To add on, acids give off a hydrogen when in water, while bases give off hydroxide in water.

Sean Wang 1F

I think we should at least know the basics because we spent a pretty long time discussing it in lecture.

Sean Wang 1F

To determine polarity of the bond, see if there is an electronegativity difference between the two atoms. If there is, then the bond is polar. Then, see if the dipole moments cancel out. If they do, then the atom is non-polar. If the dipole moments do not cancel out, then the atom is polar.

Sean Wang 1F

There are two other shapes for C3H4 in addition to the triangular shape you drew. If you google C3H4 online, you should be able to find two other shapes. One of them has a triple bond and the other has two double bonds.

Sean Wang 1F

Yes, both bonds are lone pairs are considered areas of electron densities. Even though there are more electrons in double and triple bonds, they are still considered only one area of electron density.

Sean Wang 1F

Yes, you're exactly correct! After finding the molecular formula from percent composition, you can then draw the lewis structure.

Sean Wang 1F

I would suggest redoing textbook problems that you found difficult when studying for the past 2 midterms.

Sean Wang 1F

Yes, and to add on, you find the most stable structure by calculating the formal charges of the atoms.

Sean Wang 1F

Personally, I felt that the textbook problems and attending the workshop review sessions the weekend before the exams were extremely helpful.

Sean Wang 1F

MgS would have more covalent character than MgO because the electronegativity difference between MgS is smaller than between MgO.

Sean Wang 1F

For the radical ClO, how do we know if the unpaired electron is on the chlorine or oxygen?

Sean Wang 1F

Can expanded octets be expanded even further past 10 valence electrons to like 12,14 or can valence shells only be expanded to 10.

Sean Wang 1F

Why aren't hydrogen bonds present between CH3CHO molecules?

Sean Wang 1F

I'm not entirely sure if we'll be given one for the midterm, but if we are it'll probably be on Dr. Lavelle's website like the equation and constants sheet was.

Sean Wang 1F

You need 2 electrons to fill the first period, 8 electrons to fill the second, and 8 more to fill the third. Since Cl is in the third period, 2+8+8=18.

Sean Wang 1F

I usually watch Crash Course videos if I need more help understanding it conceptually.

Sean Wang 1F

I'm not entirely sure but I looked it up online and it says that the value is 1/2 because because a particle needs to be fully rotated twice before having getting to the same initial configuration.

Sean Wang 1F

My TA said that we should know the general idea of f orbitals but that we should just focus on the s,p,d orbitals for the next midterm and final.

Sean Wang 1F

Yep, thats right!

Sean Wang 1F

Other exceptions to the octet rule can occur when the formal charge of the compound can be brought closer to 0. The closer the formal charge of the compound is to 0, the more stable the compound is.

Sean Wang 1F

Ions having the same total amount of electrons causes some similar properties, but they still have mostly dissimilar properties due to the elements having differing amounts of protons and neutrons. These protons and neutrons cause differing interactions between each other and electrons causing diffe...

Sean Wang 1F

NH3 is considered a lewis base because it acts as an electron donor when it donates a lone pair of electrons to BF3.

Sean Wang 1F

Hydrogen is unique in that it shares properties of both group 1 and 17. The position of hydrogen is not always the same between textbooks because hydrogen doesn't fit cleanly into either group 1 or 17.

Sean Wang 1F

I like to watch netflix, play videogames, and play tennis.

Sean Wang 1F

Sunday Night

Sean Wang 1F

I don't think we need to know all of the exact cutoffs for each EM, but I would know that the wavelength of the visual region is 400-700 nm and know the order of the other EMs from increasing to decreasing wavelengths.

Sean Wang 1F

Does atomic spectroscopy support the wave or particle model of light?

Sean Wang 1F

^^ Yes, that is what my TA also said.

Sean Wang 1F

Are all of the fundamental topics in the textbook going to be on the midterm like precipitate reactions and solubility rules or just the topics covered in the audio visual/textbook problems?

Sean Wang 1F

I think most of the chemical equations will be given, but I would know the common ones like the diatomics just in case.

Sean Wang 1F

Chemist: Hey girl, are you made up of copper and tellurium?
Girl: No, Why did you ask?
Chemist: Because you are Cu-Te

Sean Wang 1F

Why are 1 electron systems like Hydrogen degenerate unlike multi-electron systems?

Sean Wang 1F

In Dr. Lavelle's email, he said Bookshelf App = Great Ebook! Read this link to download the Ebook at Sapling website: https://macmillan.force.com/macmillanlearning/s/article/Sapling-Learning-Download-new-e-book-to-read-offline After installing the Bookshelf App, then click “Read offline with the Boo...

Sean Wang 1F

For Dr. Lavelle's lectures he is using the e=-hr/n^2 equation where r=3.29 x 10^15. A different equation,1/lambda=r((1/n^2)-*1/n^2) equation uses r=1.097 x 10^7.

Sean Wang 1F

I personally like using an iPad to take notes because it lets me copy paste pictures and diagrams from google instead of trying to draw them in the middle of lecture.

Sean Wang 1F

I just bought this webcam ($22) on amazon that came with a 10% off coupon code.
https://www.amazon.com/Webcam-Microphon ... 509&sr=8-4

Sean Wang 1F

I've been been studying by doing all of the practice problems assigned in the textbook.

Sean Wang 1F

The problem is printed incorrectly in the textbook. On Dr. Lavelle's website there is a page with all of the printed mistakes in our textbook. For this problem FeBr2 should be Fe3Br8.

Sean Wang 1F

Since you know the molar mass of the metal hydroxide M(OH)2 is 74.10 g·mol−1, subtract the molar mass of (OH)2 to find the molar mass of the unknown metal M. You should get 40.084 g·mol−1 for the molar mass of M which is very close to calcium's molar mass of 40.078 g·mol−1. You can then assume M is ...

Sean Wang 1F

Yes, include the heptahydrate when calculating molar mass and for the rest of the problem.

Sean Wang 1F

Once you determine the final molarity of the solution (0.05 M), you find the amount of moles of NH4NO3 in each 100 mL diluted solution by using M=moles/volume to get 0.005 moles NH4NO3. Then, multiply the amount of NH4NO3 moles by 2 because there are 2 moles of nitrogen in each mole of NH4NO3 to fin...

Sean Wang 1F

For non-ionic compounds, carbon is listed first, then hydrogen, then the remaining elements in alphabetical order.

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