CHEMISTRY COMMUNITY

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You also do not want to forget about the porous disk for concentration cells

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How do you derive the equation for van't hoff using delta G?

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Work is equal to 0 when the conditions are isochoric (constant volume). An example of this is a bomb calorimeter.

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It really depends on what information the problem provides you with, but one example would be if it asked you to calculate how long it takes for the reactant concentration to decrease by half. Another one would be like if they gave you the order and the actual half life, and you have to calculate fo...

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I would recommend using the ln version more because that version is given in the formula sheet

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No, the coefficients have no effect on the order of the reactant.

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Cell diagrams are anode|| cathode. In the anode and the cathode, the metal conductor is the outermost, aqueous solutions are nearest to the salt bridge (denoted by ||) and if there is a change in phase for different compounds | is used. If they are in the same phase a comma is used instead.

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In order for a cell diagram to work, you need a metal conductor. If a metal conductor isn't found in the anode or cathode, Pt is added.

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How do you find the pH from K?

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I believe that in both cases, gibbs free energy is measured in kJ overall. The only time I think Gibbs free energy is measured in kJ/mol is when you have to use the delta G reaction formula that requires the delta G (products) - delta G (reactants). The individual compounds in the reaction will be m...

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I believe that Lavelle will ask for the half-reactions to be applied more for Test 2

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In my opinion, I believe that the quizzes are typically applying the knowledge you learned in class, so I do not think that there will be a question asking you to derive an equation, but then again there is always a possibility.

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According to his website, the nernst equation will not be covered in Test 2

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Do you think he will also have enthalpy and entropy questions imbedded in Gibbs questions, since Gibbs free energy contains a formula that requires both delta H and delta S?

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It might be during our discussion session or after the lecture.

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It depends on the information you are given, and ultimately what you are solving for.

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How come in the delta S formula it is T2 over T1 and V2 or V1, but pressure is P1 over P2?

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If you are doing the hw questions on the 6th edition it will be all the homework problems he has written down up to 9.51

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I believe that all the derivations of those formulas are fair game on the midterm since Professor Lavelle went over it in class.

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Delta H refers to the change in energy/heat at constant pressure, that is exchanged between the surroundings and system. This means that if you are adding 10 J to the system, you are taking away 10 J from the surroundings (-10 J).

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My TA said that Lavelle will most likely provide the average bond enthalpies for resonance structures, as in the average of the single, double, and triple bonds, so I do not think that we will have to worry about the individual bonds.

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Is there an easier way to calculate bond enthalpies if you are only given the chemical formula without having to draw out the whole lewis structure?

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Professor Lavelle provides many resources such as Step up, Workshop, and Drop in Sessions for students to use. If you are confused about the topics and feel like you need more practice, I would recommend going to a Step up or Workshop session, since they teach the basics and provide worksheets to he...

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What is the difference between the different type of notations when it comes to enthalpy such as delta Hf, delta Hc, and delta H?

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You should only include gases in ICE tables, so any liquids or solids should be omitted. However, be careful because sometimes H20 can be a vapor, and thus a gas, so if it is in gas form, it should be included in your ICE table.

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When can we use approximations like making (x-0.89) become just x?

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Phase changes are endothermic because heat is required to break the bonds between the atoms in order for it to go from a solid to a liquid or a liquid to a gas. This is why during a phase change, the temperature does not change.

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Why do we omit water in the ICE tables?

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Yes you will be required to I think. There have been some homework problems that had more than 3 species already, so I would prepare for more on the test this week.

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How do you know when to use Kp or Kc? If the question does not specify, can you use either?

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How do we know when to use Kp or Kc? Sometimes it seems like you can use both?

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I also asked my TA about this question, and he said that R is a constant, so we should not have to worry about remembering it like how we are given constants on the constant wkst.

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R is gas constant, but the units can be different like atm, torr, or bar.

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Are we required to memorize the charges on the different ligand compounds or will the test give us the charge?

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Is the intermolecular force, LDF, found in all molecules?

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On question 17.33, it asks whether the compounds are polydentate ligands, and if they are, to give the max number of places the ligand can bind to the metal atom. How do you determine the max number of places a ligand can bind to the metal atoms?

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On the midterm, there was a question that asked for the bond lengths of NO2-. I got the structure correct, but can someone tell me how to find the bond lengths?

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In class, we were taught the VSEPR notation to determine the molecular shape, however are we required to learn the VSEPR notation or if we were taught a different way can we use that method? Will VSPER notation be on the test?

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NO3- has resonance, which allows all the bond angles to be the same between the different resonance structures since resonance doesn't move the actual formation of the atoms, but only rearranges the double bonds. Since NO3- has resonance, there are three different "most stable" structures,...

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What's the difference between electron geometry and molecular shape?

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What's the different between Bronsted and Lewis acids and bases? I know that acids are electron acceptors, while bases are electron donors, however I don't know the different between the two labels of acids and bases.

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What about those that have discussion on Mondays or Tuesdays? Do we have discussion too?

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Electronegativity is the attractive force between the protons and the electrons. As the atomic radius increases, the protons in the nucleus have a less attractive force to the electrons which is why the electrons are further from the nucleus, expanding the atom, and thus electronegativity decreases....

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Resonance structures refer to different ways that we can arrange the double bonds in a Lewis structure, so this is where the double sided arrow between the different structures come in. One important thing to keep in mind is that the formation of the atoms must be the same in order for it to be a re...

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I've been to a couple of different Workshops, and some UAs have a different method of deciding which element goes in the center. Some say that you want the structure to be as symmetrical as possible, so you should be placing the atom that least occurs in the middle, whereas some say that it should b...

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I know that H, He, and B are exceptions to the octet rule, but I don't understand why they are exceptions.

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10d) Rank the following in order of increasing ionization energies: C N O F Why is the order C<O<N<F? If the period trend for ionization energy is decreasing as we go down the periods on the periodic table, and increasing as the we go from left to right on the period, shouldn't it be C<N<O<F?

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12b) Draw the lowest energy Lewis structure for ClO4- Why is the lowest energy Lewis structure have one of the three Oxygen atoms with 6 lone pairs instead of doing a double bond with Cl and 4 lone pairs like the rest of the oxygen atoms? The formal charges are the same, either Cl has -1 or the O ha...

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Should we be writing out the full electron configuration starting from 1s^2 or can we abbreviate it using noble gas configuration? Do you know if there will be a preference toward one or the other when we take the midterm or it doesn't really matter?

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It also affects ionization energy. Since ionization energy is the energy needed to remove electrons from the atom, if they are in the same period (meaning they have the same # of electron shells) then those elements that have more protons will make it harder for the electron to be removed since the ...

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So I understand that the 4s^2 has a higher energy level than 3d^10 which is why it comes after 3d^10 say in element Bromine, however for Copper's electron configuration its exception makes it 3d^10 and 4s^1, but the 4s^1 is still after 3d^10, even though 4s^1 has a lower energy level than 3d^10, why...

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in a) n=2, l=1, that means that ml=-1,0,1, but there are also different spins in electrons, so since -1,0,1 (3 options), and there's a possibility of either electron being 1/2 or -1/2 (2 options), 3*2=6. So there are 6 different electrons that can have the following quantum numbers. b) n=4, l=2, ml=...

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Test 2 will cover everything from what we learned up to last Friday's lecture. That includes Photoelectric Effect, Atomic Spectra, Wave Properties of Electrons, Quantum Mechanics (which incorporate all the important fundamental equations), and atomic orbitals. I would recommend knowing the electroma...

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In the Heisenberg equation, why is Planck's constant over 4pi?

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It really depends on your TA, but it is recommended that you do the homework that corresponds to the topic that we are studying that week. That way you are more prepared to learn new concepts that may build on previous lessons.

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There was an email that was sent out last week that said it was required to have the textbook, so is it okay if you still use the pdf version or do you have to buy the textbook?

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C is the constant for the speed of light. It is 3.00x10^8m/s. Since it is a constant, it will be given during tests, so there's no pressure to remember this value for tests.

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So in problem F.13 in the Chem textbook, it asked for the name of the compound PCl5. I was just wondering if we would be expected to know the names and the chemical formula of compounds (if only given the name) on the test this week?

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Question: "To prepare a fertilizer solution, a florist dilutes 1.0 L of 0.20 m NH4NO3(aq) by adding 3.0 L of water. The florist then adds 100. mL of the diluted solution to each plant. How many moles of nitrogen atoms will each plant receive? Solve this exercise without using a calculator."...

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For some reason, I keep getting .014 grams of HCl at the end instead of any of the options on the quiz. Please help :)

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