CHEMISTRY COMMUNITY

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k once calculated is only for that temperature, which is why we have the Arrhenius equation to help calculate the new k when temperature changes

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k is a constant for the equation so it should not change if the rxn is multiplied

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zero order reactions do not depend on the initial concentrations while 1st order reactions are directly proportional to the concentrations

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the coefficents of the balanced reaction relate the rates to each other

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Activation energy is the energy needed for a reaction to occur, so the lower the activation energy, the more thermodynamically favorable the process is

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Thermo talks about the amount of energy transferred while kinetics talks about the rate that energy is transferred

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I think we just need to memorize the normal periodic trends that we used last quarter and then we will figure out the transition metal ones based on the rxn

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This is what the class website says : "Test 2 covers all topics on Gibbs free energy and electrochemistry up to but not including the Nernst equation (which is all the new material covered in class Weeks 6 and 7)", so I think everything from after the midterm up to Monday

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oxidation loses electrons so the charge becomes more positive, while reduction gains electrons so the charge becomes more negative

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Enthalpy is a measure of heat transfer while entropy is a measure of disorder in a system

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isobaric means that the volume is still changing so you can still calculate work

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What was the chemists favorite drink?
ChemisTEA

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kJ/mol

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An isolated system is useful to calculate changes that happen based solely on the reaction and not due to exchanges with the surrounding

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Degeneracy is the number of possible states that atoms can exist in and it is related to entropy because the higher the degeneracy the more potential for disorder and higher entropy.

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When U is negative, that means the net energy is out of the system or the system is doing work on the surrounding. When U is positive, that means net energy is into the system or the surroundings are doing work on the system.

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The system gains the heat of the surroundings in some reactions but the system loses the heat to the surroundings in other reactions so the net change in heat is 0 which is why Qsyst + Qsurr = 0.

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I think we will be expected to know the basic shape of the structures but they won't need to be detailed.

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In order to get to the phase of steam, the water will have had to accumulate more heat than just boiling water thus having the capability to cause more severe burns.

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Enthalpy is heat under constant pressure, so while enthalpy can be described as a state function, heat cannot because in its general definition it can have changing pressures

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The q refers to heat but qp is enthalpy because it describes heat under a constant pressure. Enthalpy can be endothermic or exothermic, meaning qp can be positive or negative as well

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they are equal in water because they are at equilibrium

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K is the equilibrium constant, the proportion of products to reactants when the reaction is at equilibrium. Q is the reaction quotient and it show the proportion of products to reactants when the reaction is not at equilibrium.

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If a rxn completely dissociates, ie a strong acid or base, then an equilibrium arrow is not used

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You use Kp or Kc based on the other information they give you, but gases can be found using either method.

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I find the UA sessions really helpful and when preparing for tests to do a lot of practice problems, especially the ones that are integrated into the readings

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I think stick to the formulas he has given us in lecture so far, bc this one hasn't been mentioned yet.

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Aqueous substances are included in finding the equilibrium constant

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For the equilibrium constant, you only include the substances that are in the aqueous and gas phases so the inclusion of water will depend on the equation that you are looking at.

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Solids and liquid concentration can't change and so they don't have any effect on the equilibrium constant

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I think we're supposed to know the compounds in the table that Lavelle posted on the course website

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You can't determine between tetrahedral and square planar by looking at it, so if a compound has four ligands, you can label it as a tetrahedral complex or a square planar complex.

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Some other examples from problems in the book are HCO3- and HPO4^(2-)

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So what exactly is paramagnetism and diamagnetism?

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Hybrid orbitals have lower energy than their unhybridized counterparts, so I think hybridization occurs to make the compounds more stable due to lower energy pockets.

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So order only matters for electron configuration but not hybridization?

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A molecule could have a distorted tetrahedral shape due to lone pair repulsion that causes bond angles to be less than suggested by the VSEPR model

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From the course website: "Test 3 covers: End of Bonding from 3.12 (6 Ed.) and from 2D (7 Ed.); and all of Molecular Shape and Structure (see Syllabus and Outlines for details"

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Do sigma and pi bonds have a different strength or is the main significant difference the way in which they overlap?

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No, because having more than 4 single bonds would consist of an expanded octet. To have more than 4 single bonds the atom would have to be in the 3p block or higher.

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It is determined by the locations of the bonding and lone pairs and the repulsion associated with those electrons

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The updated test and exam schedule on the course website has the next test listed for the week of November 27th so it shouldn't conflict with Thanksgiving break at all :)

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At a workshop I went to, a UA said it would be a good idea to write them out but it wasn't completely necessary unless stated explicitly in the problem

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A lewis acid is an electron acceptor while a lewis base is an electron donor

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To determine which atom the unpaired electron goes on, you have to look at the formal charges and determine which atom it will make the formal charge be closest to 0

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Both mean the same thing, so using the 2 dots instead of the line would not be incorrect, but I think Dr. Lavelle uses the line because it is more convenient and clearer.

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Elements in the top right corner have the highest electron affinity but it is less periodic than atomic radius

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The central atom is generally the atom with the lowest ionization energy, which is usually furthest away from row 17 (bc atoms in row 17 typically have the highest ionization energy)

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This answer above is a great explanation!

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So lowest energy configuration means that an atom is in ground state and anything else is excited?

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Test 2 covers quantum and bond/orbital materials up until the Friday lecture of week 3.

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When energy is released, it is negative/exothermic and when energy is absorbed, the reaction is positive/endothermic

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This is very helpful, thank you for the insight!

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Dr. Lavelle said in lecture that the 4pi comes from the derivation of the equation and that it is not specifically important that we know how to find it/why it is there for this class.

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That's a really great way to explain it, thanks for that clarification.

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With bigger objects, there position is almost always measurable so their uncertainty is negligible.

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Thank you! This is really helpful for the first test!

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Bozeman Science has videos that are very similar to Crash Course that cover AP Chemistry topics.

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Such useful advice to keep in mind! Thanks!

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Combustion is just the combination of an organic molecule with O2 and it includes the products CO2 and H2O

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