CHEMISTRY COMMUNITY

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While that does make sense, Dr. Lavelle said that it just lowers the value of Ea and the equation, so I am unsure.

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Microscopic reversibility means if you do the forward process of a reaction mechanism, you will have A & B as your intermediate. If you do the reverse process of the reaction mechanism, you will still have A & B. Microscopic reversibility is when the intermediates are the same for both forwa...

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We identify a catalyst by this method:

Look for a reactant that is used and then reformed (taking it out of the overall reaction). This is what a catalyst is. It is originally there and used, but then reformed at a later stage.

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Yes this is correct, however the rate laws are always positive, that's why the - is included within the reactants.

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If you graph [R] v time & get a straight line: zero order

if you graph ln[R] v time & get a straight line: first order

if you graph 1/[R] v time & get a straight line: second order

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We covered Ahrenniu's equation, which can be found within the book.

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Integrated rate law is the rate within a time period so you can see the rate at that time, but the general rate law is just the rate vs the conc. of reactants.

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You use Kelvin because you must match the units within the R (gas constant) which uses kelvin.

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Lavelle makes the final.

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NO is the only catalyst and O2 is simply just a reactant because it is not reformed in the products.

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It won't be covered on the final. He did say there are some homework questions on it, but it is not going to be tested.

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E Is an intensive property, so you do not multiply the E value when the equation is multiplied.

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If they are highly positive, they are a strong reducer. If they are highly negative, it is a strong oxidizer.

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Salt bridges cannot be used because since it is the same molecules on both sides, the salt bridge wouldn't move anything. Porous disks allows for the higher concentration to diffuse into the lower.

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You flip the equation that is being oxidized. For a galvanic cell, the E has to be positive, so whichever will make it positive.

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For this question, delta H will be the largest for the most moles because its J/mol. Delta H impacts delta T, so B, which has the most moles, is the correct answer.

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The end of thermodynamics to electrochemistry is perfectly fine for the homework!

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When using this equation, it assumes that the pressure / volume is constant.

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This equation is used when you have a reaction at two different temperatures with two different k values. It is used to solve for T2/K2 or T1/K1

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While the final exams are not curved, I do believe that at the very end, it depends on whether or not the top person did in the class to determine the grade of everyone else.

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G Knot is for when the things are at standard state in the world. G is just the G at that specific states.

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Yes, it is given on the formula sheet. It is the Blotzman constant.

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Intensive properties do not rely on the quantity of matter while extensive properties due depend on the quantity of matter.

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Constant volume uses Cv and Constant pressure uses Cp. Cv is normally used though.

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Nope, Delta H is always equal to q, but q is not always equal to Delta H. Therefore, Delta H is only equal to q when p is constant.

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WE set delta G to zero in the practice problem because by setting it to 0, it gave us the minimum temperature needed to make the reaction spontaneous, therefore answering the question.

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When w is positive, work is being done on the system & when w is negative. the system is doing work. For example, today the system pushed the piston outwards, doing work on the system, making w negative.

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You just need to know that if pressure is constant, the integral results in P (delta)T & if pressure is not it results in nrtln(v2/v1).

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Heat capacity is the amount of heat required to raise 1g of substance up by one temperature.

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For the system as a whole, there cannot be an exchange in energy because its isolated so the energy is constant.

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Breaking a bond requires energy to overcome the bond strength while forming a bond requires energy to be released.

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The normal method would be Method 1. It has the exact enthalpies and would give you the right answer. When doing bond enthalpies, its different because each molecules would have different and its jut an average. So method 1/3 are the best.

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Yes, temperature is a factor that changes the equilibrium constant. For example, if temperature increases in a reaction, the equilibrium constant will change.

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Test 2 will only cover the information that comes after the midterm and up until test 2!

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No, instead of multiplying, you add the enthalpies together. If its reverse, you just switch the sign of the enthalpy, and if you double it, you double enthalpy! Hope this helps.

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In multi-step reactions, the enthalpies are able to be added together because enthalpy is a state function (meaning the path to get there doesn't matter, its just the value). So you need to just add the enthalpies together.

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You use an ice table to calculate the concentrations of all molecules in a reaction at equilibrium. You set up the table with Initial, Change, Equilibrium going vertical and the molecules involved in the equilibrium constant going horizontally. You list the initials, the changes, and then the equili...

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R is the universal gas constant and has the units of the other variables (L, atm, etc...)

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It depends on which side of the equation has more moles of gas. If the reactants have more moles of gas and pressure is increased, the reaction will shift to the right to lower the pressure and re-reach equilibrium.

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We use the quadratic equation in terms of chemical equilibrium when we are estimating the equilibrium point of a reaction through an ICE Table. If we are unable to use the "x is small" approximation, you must then use the quadratic equation to solve for x.

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In an endothermic reaction, heat is technically considered a reactant because it takes heat to cause the reaction to occur.. So I we add more reactant, it will force equilibrium to shift to the right, creating more product.

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Yes. Exactly that. If the reaction is shifted to the left, more reactants are created and if the reaction is shifted to the right, more products are formed.

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When the pressure is decreased, the reaction will proceed in the direction that has more moles of gas because it will want to increase the pressure to re-reach equilibrium.

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K has no units as hen you do all the calculations, the units cancel out. Furthermore, this is because K is just a constant.

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Solids & liquids are excluded when solving for Kc. Only gases and aqueous solutions are included.

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Q is just the system quotient at any time. If q ends up equaling K that means that the reaction is at equilibrium. If K>Q the forward reaction is favored & if K<Q then the backwards reaction is favored.

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Yes. All gases should be included in the equilibrium constant.

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If the question asks you to solve for the equilibrium constant, that is when you use Kc. If the question asks you to determine whether the reaction is at equilibrium or will proceed forwards/backwards, that's when you compare Kc to Q

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A change in pressure & or volume results in a change in the opposite. These just cause the reaction to go forward or backward and then eventually re-reach equilibrium. Temperature causes the molecules to speed up while nothing else is changing, causing more of them to hit each other.

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Yes. Q and Kc are solved the completely same way. Q is just to tell if the reaction is at equilibrium or not.

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There are no units for K as the units tend to cancel out.

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H20 + CO2 -> H2CO3

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Yes. Dipole-Dipole IMFs means that both of the molecules have a dipole moment.

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A triple bond has a hybridization of sp because the central atom (which will have one triple bond and one other area of electron density) creates two areas of electron density, which has the hybridization of sp.

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When a hydrogen absorbs, the energy is positive because it is adding it to the molecule, requiring energy.

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A double bond has nothing to do with melting point because melting point has to do with intermolecular forces rather than molecular bonds.

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Ka is the disassociation factor while pKa is the pH of the Ka factor. For example. If an acid has a pKa of 1.0x10^-7, the pKa will be 7.

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Cis & Trans relate to when the same molecule just has different bonding sites for outer elements. Trans is when they are diagonal and Cis is when they are on the same side. This is extremely important to biological compounds as it can totally change the function because shape is influenced. Howe...

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Week 9 homework is on Coordination and Biological Compounds & the beginning of Acids/Bases.

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Dispersion occurs between two non polar molecules. When two non polar molecules get close into contact, the electrons will cause an induced-dipole onto both molecules, making one side positive and one slightly negative. This yields them to be attracted to each other, creating LDF aka dispersion. H b...

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Sigma bonds can be rotated amongst their axises & orbitals, while pi bongs cannot. Sigma bonds are always formed first before the pi bonds, signifying why a single bond only has one sigma bond and no pi bonds. However with double and triple bonds, there is only one sigma bond and two pi bonds.

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S orbitals are the only orbital that are unable to form pi bonds because they can rotate no matter what due to the spherical structure. P/d/f orbitals can form pi bonds because they can form double and triple bonds. Therefore, yes, f orbitals can contain pi bonds.

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Officially, FeO2 is considered a polar covalent bond. However, it shows extreme ionic character due to the electronegativity difference (~1.6).

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Hybridization is not on the test, but the pi and sigma bonds will be discussed about in a small section of lecture on Monday. They will be on the test.

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An electrostatic potential is just a synonym of electric field. Electric fields contain both positive and negative parts. Therefore, a polar molecule, which has both positive and negative side, will be attracted to an electric field.

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Dr. Lavelle said that Radicals (meaning the lone electron that is not in a lone pair) counts as one area of electron density. Due to this, in VSEPR Theory, one electron is equivalent to a double bond and a single bond and a lone pair.

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While the bond angles and shape do not have to be drawn correctly (because you can tell the shape based on bonding pairs / lone pairs), it would be extremely helpful to draw them as close as possible. If the question specifically asks for the lewis structure, then it does need to be drawn correctly.

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Dr Lavelle has not released them. He will most likely release the dates & times for them around a week prior to the test. Watch out as they will be coming soon!

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A temporary dipole is a dipole created by a non polar molecule. For example N3 which has two Nitrogen atoms triple bonded to each other (both with one lone pair) can create a temporary dipole on itself do to electron dispersion. The e- will not always be completely stable, so sometimes one of the N'...

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Some examples include: I, Xe, S, etc...

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The equation is used at any time you are asked the wavelength of a particle with mass. Whether it is a baseball or neutron, both contain mass and follow the De Bregolie equation.

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Personally, I believe that the test will cover two more topics: Molecular Structure/Shape & Coordination Compounds & their biological importance, But I do not know. We will have to wait and see. It will not cover any topics that were on the midterm though.

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The reason that CO is more polar than BO is due to the electronegativity difference between both elements. CO has a great electronegativity difference, so it is more polar than BO.

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The resonance structure is the same exact structure, but the double bond with the O and N is just placed with the second oxygen attached to the [N]

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Some factors impacting the energy of electron in a multi-electron atom are:

Electron-Electron repulsion
Shielding
Penetration
Zeff

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We would not need to memorize this. You find out the ionic character through the electronegativity difference. The difference between c is 1.39, and typically, anything equal to or less than 1.5 is determined to have more covalent character.

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Hello! This is kind of something that you have to get the hang of, but you can tell that the H is going to be attached to the Cl because of how the molecular formula is formatted. HCl, a common known molecule, is together. If the H was attached to the central atom, then the Cl would have probably be...

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These are the lengths of both bonds. The double bond is shorter than the single bond because double bonds are stronger, holding the two atoms closer together, decreasing the distance.

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The kinetic energy equation will be supplied, but you should know how to use it and what the results means.

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Nodal planes are where the electron density is zero. This means that there are absolutely no electrons there.

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S-block elements tend to be a lot more reactive than p-block due to their ability to remove electrons with ease. This allows them to share them with other elements, making them really reactive, while p-blocks do not like to lose electrons, making their reactivity much lower.

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5s2 would lose an electron first because it is considered the furthest one out. 4d10 is not part of valence electrons once you have 5s2.

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There are only two electron spins. One is going clockwise and the other is counter clockwise. Two electrons paired by Hund's Rule will have opposite spins.

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The reason we fill up all the parallel electrons first is a) because of electron-electron repulsion and b) an atom wants to be the most stable. If you fill up pairs first, the atom will not be as stable as it would be when filling up separate parallel electrons.

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The only reason that we move an electron from s to d is because the energy difference is not as large, but it makes the atom more stable that way. By removing an atom from the s and moving it to the p orbital, the energy difference would be much larger and the end product would be more unstable than...

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Attend step-up sessions, but also do not over extend your mind. Study a little day by day until you are understanding it more and more. By this, you will soon be very prepared! Good Luck!

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To decide how many sig figs you need to use on the test, look at the problem and see which number has the lowest amount of sig figs. Your answer will have the same as that. Furthermore, some TA's are lenient when grading. Ask them what they think.

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When they have parallel spins, they repulse each other because they both are negatively charged. Kind of like how to south sides of magnets repel each other.

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Effective Nuclear Charge is really important for ionization energies too. If an element has a higher ENC, then the nucleus will hold onto electrons harder, requiring more energy to remove them

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keV is an interesting unit. 1 keV is about 1.602x10-19 J.

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The uncertainty value is 0.2 because you add .1 and subtract .1 from the given value, giving a total uncertainty value of 0.2.

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The uncertainty value is 0.2 because you add .1 and subtract .1 from the given value, giving a total uncertainty value of 0.2.

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The unit for Hz, which is a frequency is s^-1. However, it means cycles per second.

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The following are conserved:
Mass
Atoms
Electrons
Protons

All must be conserved in order to have a complete chemical reaction.

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3.00 x 10^8 is acceptable to use in almost all cases since we do not need the specificity that the actual number implies. In a case where any said number could change the result and have a large effect, then you would use the 2.9 value, but we do not have that in this class.

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Within your work, follow the sig figs, but when using your calculator, do not cut off the rest of the numbers. It will seriously skew your results.

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These concepts, to my knowledge, are not related. The reason that were reminded of those two equations were because as the variable -> infinity, the result of the equation -> 0. While the two concepts are similar, they are not related. Just a coincidence.

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The Rydberg formula does not give the best explanation for its own use, however, it is one specific scenario. If you are given an electron that jumps from one level to another, and you are told to find the frequency, you can find it easily with that equation.

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As of right now, they do not matter as much, but in the future they will matter a lot. They are really telling, especially when we get into deeper chemical equations. It is also super helpful for when we do lab and see what state of matter we need to expect.

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There can only be one or zero limiting reactants. If there were two limiting reactants, both would be in perfect amounts, or perfect proportions, fully completing both amounts of reactants. Therefore, there can only be one. When there is no limiting reactant, it is known as a complete reaction.

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