CHEMISTRY COMMUNITY

faithkim1L

Open book is pretty every resource you can lay your hands on. I don't think he will be using Respondus or another program to record us while taking the exam, so I think textbook, notes, and other instructional notes are all fair game for "open book."

faithkim1L

Lavelle has not mentioned much about the final, other than the content and the fact that it will be take-home. He did state that he will send out another email and directions soon. I think we'll have more information towards the end of the week and just need to sit tight.

faithkim1L

He hasn't mentioned the exact format or the directions for the final. Judging from his other tests, I would expect there to be some calculations, but the final may be a similar format to the modules. I honestly have no idea, but he said he would be posting and sending directions in another email thi...

faithkim1L

The format isn't known. From his past tests and exams from Chem 14A and Chem 14B, I don't think so. But he did state that it will be more straightforward and simple.

faithkim1L

My TA emailed me about locations and pick-up dates. If he/she hasn't done so yet, it would probably be best to email your TA and ask about it.

faithkim1L

An electrode is a metallic conductor that is in the electrolyte solution. This allows electrons to flow between the two solutions. Platinum is really common for this. Graphite is also used, but not nearly as common as Platinum.

faithkim1L

Use Ecell = Ecathode - Eanode... in a galvanic cell, make sure that Ecell is positive, so the cathode needs to be more positive and the anode more negative.

faithkim1L

Q is the concentration of products divided by the concentration of reactants. Put the coefficient as the exponent for the concentrations of products and reactants.

faithkim1L

n is the number of electrons transferred in a redox reaction.

faithkim1L

When balancing acidic reactions, add H+ and H20. For basic reactions, add H20 and OH-.

faithkim1L

Usually you use Pt as an electrode in the diagram if there is no solid present for either the anode reaction or the cathode reaction. Lavelle mentioned that graphite can also be used, but it's not nearly as common as Platinum.

faithkim1L

An oxidizing agent is the thing being reduced, and a reducing agent is the thing being oxidized. I just remember it as the reverse since it can get a little confusing at times.

faithkim1L

H+ is for acidic reactions, and OH- is for basic reactions. H20 is used in both acidic and basic reactions.

faithkim1L

OH- and H+ can be added on either side. Remember OH- is for basic solutions and H+ is for acidic solutions.

faithkim1L

Differential rate laws will show rate as a function (the dependent variable) as a function of the reactant's concentration [R] (independent variable). Integrated rate laws will show reaction rate (dependent variable) as a function of time (independent variable).

faithkim1L

In acidic redox reactions, you use H+ to balance the hydrogens in the reaction. In basic redox reactions, you need to use H20 and OH- in a sort of back-and-forth balance. Basic reactions have an "extra step" where you can't just balance O and H with H+ and H2O.

faithkim1L

The salt bridge allows ion transfer across the two solutions. If there is no salt bridge, the reduced and oxidized solutions will continue to get charged as the reaction occurs.

faithkim1L

From what I remember, I think the problem will usually state whether the reaction takes place in basic or acidic solutions.

faithkim1L

Platinum is an inert conductor used to transfer electrons. It's an electrode that's placed on the reductio side.

faithkim1L

Platinum is the most common electrode used in electrochemical cells. It' resistant to oxidation and won't easily react in redox reactions. Pt is an inert conductor which is used to transfer electrons. Lavelle also stated that graphite can also be used I believe, but is not nearly as common as Platin...

faithkim1L

Yes. An oxidation reaction means that there is a loss of electrons, which just be written on the product side.

faithkim1L

Yes. Remember STP is standard temperature and pressure, which is temperature (273.15 K) and standard pressure (1 atm).

faithkim1L

In a reversible isothermal reaction, the total S is zero.

faithkim1L

I believe this is because there is no external pressure pushing the piston in, so there is free expansion (the system can do work freely).

faithkim1L

Oxidation is when the reactant will lose an (or more than one) electron. Reduction reactants will gain electrons during the reaction. LEO GRR is really helpful for me.

faithkim1L

When Lavelle uses Rev, it means that the reaction is reversible.

faithkim1L

The equation sheet on the website will be the equation sheet given on the midterm. He also uses the IUPAC periodic table, but it dates back to 2011 or so I believe. The molar masses are slightly different than the ones he uses in class (he uses different periodic tables), so be careful on tests.

faithkim1L

Lavelle doesn't give out distribution curves for the test. He does provide the average on the midterm and final.

faithkim1L

Lavelle does grading on a point system.

Test 1: 50 points
Test 2: 50 points
Midterm: 120 points
Final: 180 points
Homework (5 points per week): 50 points
Chemistry Community (5 points per week): 50 points

Total: 500 points

IF he decides that he is going to scale the class, he does so at the end.

faithkim1L

The standard entropy of a substance increases with an increase in the molar mass. But I also think that the standard entropy of a gas at STP takes in a lot of factors of phase change and heat capacities of solids and liquids as well.

faithkim1L

Yes. I also believe you can do the problems from other outlines as well, since the midterm is coming up.

faithkim1L

Do we need to know the integral and derivative for the midterm?

faithkim1L

Delta H should be positive.

faithkim1L

Constant external pressure.

faithkim1L

101.33 Joules converts to 1 atm Liter-atm.

faithkim1L

State functions don't depend on the path taken to get to its current state. The formula final - initial works for state functions, meaning that the stuff between final and initial doesn't matter. Enthalpy is a state function.

faithkim1L

During a phase change, the temperature doesn't change because the energy (in the form of heat) is being used to either weaken (melting) or break (vaporization) the bonds between molecules.

faithkim1L

H2SO4 is a strong acid, meaning that we can assume that it dissociates completely. Therefore, we know that the eq concentration of products will be the same as the initial concentration of the reactants (H2SO4). Calculate pH using the formula: -Log[H3)+] = pH.

faithkim1L

1) ICE Table to determine [H3O+]
2) -log [H3)+] = pH
3) 14 - pH = pOH

faithkim1L

A state function is determined by the current equilibrium of the reactants and products, meaning that the path taken to reach that current state does not matter. Basically, it means final - initial is a valid calculation for enthalpy.

faithkim1L

The K value you used was probably incorrect. When you look at table 5G.2, there are multiple K and Kc values for each equation. The second column (the first one with the numbers) is the temperature. The K you used, 794, is for the reaction taking place at 298 K. In the problem, it is 500 K and the K...

faithkim1L

An ICE table is used for equilibrium concentrations when we are unsure of the amount of change (in molarity) in the reactants as the chemical reaction moves to equilibrium. I stands for initial, which are the molarities that are given. Sometimes, the problem will only provide the moles and the conta...

faithkim1L

When Kc is a very small number, we know that there will be a large amount of reactant and a small amount of product (Kc is products over reactant, so the larger the denominator the smaller Kc). When Kc is 10^-3 or smaller, we can assume that the change (x) is so small that is makes a negligible effe...

faithkim1L

First, convert moles given to molarity. It's a 10.0 L container, so the molarities of N2 and O2 are .0482 and .0933 respectively. With the equation given, Kc = [NO2]^2/[O2][N2]^2 Create the ICE table. N2 O2 N2O I .0482 .0933 0 C -2x -x 2x E .0482 - 2x .0933 - x 2x Kc = 2.0 x 10^-37 Kc = (2x)^2/(.933...

faithkim1L

When you calculate Q, you use the exact same process as if you were calculating for K. This means that you include all aqueous solutions and gases. Do not include solids or liquids in your calculations for Q (or K for that matter).

faithkim1L

First, you create your ice table. SO2. O2. SO3 I. .522 .633 0 C. - 2x -x 2x E. .522 - 2x .633 - x 2x Then, set up Kc and put in all the numbers/expressions. Kc = 5.66 x 10^-10 Kc = [SO3]^2/[SO2]^2[O2] 5.66 x 10^-10 = ((2x)^2)/(.522-2x)^2(.633-x) *Since Kc is so small, we know that the equilibrium re...

faithkim1L

R is the gas constant. I believe it will be given on the equation/constant sheet on tests.

faithkim1L

Le Chatelier's Principle basically just says that a chemical equation will move to decrease the amount of change as much as possible. So if there is a chemical equation and product has been added, the equation will move "away" from the products and towards the reactants (reverse reaction).

faithkim1L

Kp is used for gases. Kc can be used for aqueous solutions. It's best to just go by the equation. Remember Kp is in pressure units and Kc is for concentration (M).

faithkim1L

Most TAs correct HW based on correctness and completion. There is the answer solution book to check answers, and just make sure you do five problems a week.

faithkim1L

Homework is usually due during discussion, but for the first week it was due after lecture on Friday.

faithkim1L

As long as the ratio is the same as the ratio of the balanced equation, it doesn't matter what the actual numbers are.

faithkim1L

I think we only need to know the concepts and the logistics of Ka, but we won't have to do any calculations since we haven't learned everything about weak acids. We will, however, need to know about strong acids and its dissociation properties.

faithkim1L

I think most of it is conceptual. Titrations allow us to find the molarity of an unknown solution using another solution with a known molarity. We use the stoichiometric point/equivalence point to figure out the molarity of the unknown solution.

faithkim1L

Amphiprotic means that the molecule can accept or donate an H+. Amphoteric means that the molecule can can act as a base and an acid. If a molecule is amphiprotic, it's amphoteric, but it doesn't necessarily work the other way (think Lewis acids - relationship with electrons).

faithkim1L

The pH would only be negative if it's a super acid. In these cases, Ka is larger than 1. I don't think we need to know this for the final though.

faithkim1L

Dirty coal has a larger amount of S in it. I think that's all we need to know.

faithkim1L

I think practice problems are a really good idea, on top of maybe some reinforcement through the step-up sessions and online videos.

faithkim1L

There are solubility rules that help you identify which ones will dissociate in water and become aqueous, and those that will not. The best way to know is just to memorize the solubility rules. It was mandatory in HS AP Chem to know them, but I'm not sure if Lavelle will have us memorize them too.

faithkim1L

Drawing net dipoles helps a lot, but you need to make sure that you are not just cancelling dipoles that seem opposite each other. For example, in CHCl3, you can't cancel the dipoles of Cl that are across from each other, because the bond angle is actually 109.5 and not 90/180. Also, when there is a...

faithkim1L

Doing practice problems really help. It's the best way to get used to the types of problems that will be on the test, and it will also reinforce the concepts that you're learning for the test.

faithkim1L

The bond angles for the seesaw molecule will be slightly less than 90 and 120 degrees, since the lone pair affects the bonding angles.

faithkim1L

Anything inside the brackets are part of the main coordination compound.

faithkim1L

A Bronsted acid is a proton donor while a Lewis acid accepts an electron pair.

faithkim1L

Because there is a lone pair, the angles should be slightly less than 90 and 120.

faithkim1L

When you draw the bonds, you draw them as normal and just label each bond below or beneath the bond with a pi or sigma symbol.

faithkim1L

When there is only an X or an E, it is implied that there is one of those.

faithkim1L

It allows you to picture the molecule, allowing you to know how many pairs of lone pair electrons there are and how many atoms the central atom is bonded to.

faithkim1L

Hydrogen bonds only form between H atoms and N, O, and F.

faithkim1L

We don't have to memorize the electronegativity chart. It's easier to use the net dipole to figure out if the molecule is polar or not. For example, for CH3Cl, there is a net dipole towards the chlorine atom, making the whole molecule. However, for CH4, there is no net dipole which makes the molecul...

faithkim1L

Sigma bonds are the first bonds between any two atoms. So, for single bonds, there are only sigma bonds. However, for double and triple bonds, pi bonds are the other bonds (2nd and 3rd bonds) formed between two atoms. So for a double bond, there will be one sigma bond and one pi bond. The pi bonds a...

faithkim1L

If I remember correctly, hybridization will not be on Test 2. The test covers material from the midterm on. The lecture on Monday, about sigma and pi bonds, will be on the test.

faithkim1L

The angles for the molecular shapes are all standardized. When a molecule is polar, the bond angles will change, but we do not need to know the exact values. All we need to indicate is that the angles either decrease or increase (i.e. with lone pairs of electrons instead of bonding pairs).

faithkim1L

London Dispersion Forces (LDF) are classified as universal because any molecule or atom with any number of electrons will experience some kind of movement. Since electrons are not in a "fixed" position (they are in an electron cloud and move around there), there will be some areas that are...

faithkim1L

The modules on Lavelle's website are extremely helpful, especially when you just want to go over the concepts that you went over in class. Also, the step up classes are helpful and office hours are too. I recommend just going through a lot of the chem problems from the textbook (the odd ones, since ...

faithkim1L

When you draw the lewis structure for both AsF3 and AsF5, the former has a lone pair of electrons over As. This results in polarity, and there are dipole-dipole moments in the molecule. However, in AsF5, there are no lone pairs on As, meaning that the whole molecule is nonpolar and has no dipole-dip...

faithkim1L

Hydrogen bonds are the strongest IMFs. They are significantly stronger than London Dispersion Forces because those are only temporary and are not necessarily "permanent." They tend to move around more than hydrogen bonds, which are usually always polarized.

faithkim1L

It's really nice to know the conversions at the top of your head so you're not looking around the reference sheet for them. However, I believe Lavelle is quite generous and provides most of the formulas and conversions for the exams.

faithkim1L

Charged molecules are completely bracketed with the total charge written outside in the top right corner outside the brackets.

faithkim1L

Elements in or after the third period have expanded octets. The central elements usually end up with the expanded octets (the extra pairs of electrons).

faithkim1L

All the chemistry jokes argon!

faithkim1L

When a molecule has resonance, you usually have to draw all the possible structures.

faithkim1L

Br has an expanded octet in this case. Any element in or after period 3 can have an expanded octet.

faithkim1L

Covalent bonds share electrons across the elements in the molecule. In ionic bonds, the cation "gives" its electron(s) to the anion.

faithkim1L

l=0; s
l=1; p
l=2; d
l=3; f

faithkim1L

Sapling Learning is a good resource to use other than the midterm review sessions. Doing all the recommended practice problems on the outlines is also really helpful.

faithkim1L

Studying chemistry is really just practice. I find it best to do practice problems. Lavelle's Step Up Program is also really helpful if you're struggling with the material in general.

faithkim1L

Valence electrons are the number of electrons in the valence (last) shell of the atom. For example, Cl has 7 valence electrons.

faithkim1L

Cu and Cr are the only exceptions.

faithkim1L

I am pretty sure that these are provided on the 'reference sheet' that Lavelle gives us. It will probably be similar to the one on the first test we took Week 3.

faithkim1L

In multi-electron atoms, there is a shielding effect that causes the outer electrons to be 'shielded' from the nucleus by the inner electrons. Because of this, there is a lesser attraction between the outer electrons and the nucleus, and this results in a larger atomic radius.

faithkim1L

It's very helpful to know the basic conversions, especially the metric system (because they're all multiples of ten). However, I believe that on the tests, Lavelle provides some of the conversions as a reference sheet.

faithkim1L

When shortening the electron configuration to make it easier to sort through, people use the noble gas and write out the last line of the electron configuration. However, you can also just write out the whole thing.

faithkim1L

The answer depends on each problem. Avogadro's number represents the number of (mcls, atoms, ions) per mol of the given element or compound.

faithkim1L

Black body radiation is not necessary to the course. It's more of a physics experiment.

faithkim1L

Yes, this is correct. The light intensity is directly related to the number of photons.

faithkim1L

There is no maximum to the number of energy levels. But in the diagram that is drawn in class, the energy levels get closer and closer together.

faithkim1L

An electron is excited and rises to a higher energy level. However, electrons can release energy in the form of a photon. This will cause the electron to eventually fall back to its original state.

faithkim1L

Frequency and wavelength are inversely related. So if frequency increases, then wavelength decreases. Frequency is in Hz (s^-1), and wavelength is usually in nm. However, if you're finding wavelength to put it into another equation, make sure the units cancel out.

faithkim1L

The best way to ensure that you will end up with whole numbers on all of the stoichiometric coefficients is to multiply all the coefficients by the common denominator of the fractions. For example, if you had two fractions as stoichiometric coefficients with the denominators 2 and 3, you should mult...

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