CHEMISTRY COMMUNITY

Kaylee Sepulveda 4G

A few moles of lithium hexafluorophosphate were sentenced to five years in prison.

They were charged with a salt in battery. :)

Kaylee Sepulveda 4G

What happens when oxygen atoms get haircuts?

They donate their lone hairs :)

Kaylee Sepulveda 4G

Each approach varies in usefulness depending on the context of the problem, the complexity of the reaction, and what information is provided. The differential rate law approach expresses the reaction rate in terms of changes in the concentration of one or more reactants (Δ[R]) over a specific time i...

Kaylee Sepulveda 4G

A pseudo-first-order reaction is a reaction which is not a first-order reaction naturally, but is made first-order by increasing or decreasing the concentration of one or the other reactant. This article provides an in-depth explanation with examples: https://chem.libretexts.org/Bookshelves/Physical...

Kaylee Sepulveda 4G

Thank you for everything you've done these past two quarters, Dr. Lavelle! I know this situation was very unexpected and difficult to manage, but I think you handled it wonderfully.

*high five* :)

Kaylee Sepulveda 4G

A second-order reaction (where order = 2) has a rate proportional to the concentration of the square of a single reactant or the product of the concentration of two reactants. The formula is: rate = k[A] 2 (or substitute B for A or k multiplied by the concentration of A times the concentration of B)...

Kaylee Sepulveda 4G

If we covered the derivation in class, or it is mentioned specifically on the course outline (a few derivations are mentioned explicitly), they are "fair game", as Professor Lavelle likes to put it.

Kaylee Sepulveda 4G

Thermodynamics is not about things moving and changing but instead about how stable they are in one state versus another, while kinetics is about how quickly or slowly species react. Thermodynamics-VERSUS-Kinetics.jpg I think you might need to take a look at the lesson outlines but here are some equ...

Kaylee Sepulveda 4G

An article I read said that ATP could be analogously described and 'rechargeable batteries.' The batteries are used, giving up their potential energy until all of it has been converted into kinetic energy and heat(unusable energy). Recharged batteries can be used only after the input of additional e...

Kaylee Sepulveda 4G

"Electroplating is a process that uses electric current to reduce dissolved metal ions by the use of electrolysis, to obtain the dissolved metal ions at the other electrode, mostly in the form of a uniform coating." This article explains the concept in more detail: https://byjus.com/physic...

Kaylee Sepulveda 4G

Unless it specifically asks for Q_p or Q_c, I don't think you need to convert anything. And typically you're going to be given partial pressures for gases and concentrations for aqueous solutions, which I believe was the case in the problem you provided as an example.

Kaylee Sepulveda 4G

When solving this problem, you are given that the E° (cell potential) is equal to -0.689V Since we know that Cu/Cu 2+ is the anode, M 2+ /M is the cathode. Since E°= E° (cathode) - E° (anode) and the table gives us E° (anode) = +0.34V We just plug in the values: -0.689V = E° ...

Kaylee Sepulveda 4G

The idea of the universe's eventual heat death suggests that the universe will eventually evolve to a state of no thermodynamic free energy. Therefore, it would be unable to sustain processes that increase entropy. Once we reach this maximum entropy, no more work can be extracted from the universe. ...

Kaylee Sepulveda 4G

The order of reaction can be found experimentally by changing the concentration of reactants and observing the change in the rate of reaction. For example, if doubling the concentration of a reactant doubles the rate of reaction, the reaction is a first-order reaction for that reactant. rates.png ze...

Kaylee Sepulveda 4G

Usually, if you have something on both sides of the reaction (i.e. it is not being changed in any way and isn't really part of the reaction) you want to cancel it on both sides to simplify your final redox reaction.

Kaylee Sepulveda 4G

Boltzmann's equation is an equation relating the entropy S of an ideal gas to the quantity W, the number of real microstates corresponding to the gas' macrostate: S = k_B ln W
where kB is the Boltzmann constant (also written as simply k) and equal to 1.38 × 10⁻²³ J/K.

Kaylee Sepulveda 4G

This is because endothermic means a process or reaction that absorbs energy in the form of heat. To break a bond would require heat to be inputted as a reactant

Kaylee Sepulveda 4G

Kaylee Sepulveda 4G

Most of the equations you'd need to know on an exam would be given on the constants/equation sheet, or could be derived from a different equation that is given. This article explains the Van't Hoff equation in a bit more detail: https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemis...

Kaylee Sepulveda 4G

The purpose of the salt bridge is to maintain charge balance as the electrons are moving from the anode to the cathode.

Kaylee Sepulveda 4G

Standard entropy means the entropy of a certain substance under standard conditions. They would usually be given in a table format (like we saw on the midterm, we were given the standard molar entropy of different molecules) Here is a brief article explaining it: https://chem.libretexts.org/Bookshel...

Kaylee Sepulveda 4G

The short answer is that it makes it easier to balance the equation (keep in mind charge is important now as well as stoichiometric coefficients) Here is an article that goes more in-depth and provides some examples: https://opentextbc.ca/chemistry/chapter/17-1-balancing-oxidation-reduction-reaction...

Kaylee Sepulveda 4G

Heat capacity is a state function, but heat capacity is an intensive property. In contrast, specific heat capacity and molar heat capacity are extensive properties. Extensive means that it depends on the amount of material being affected, so mols or grams would be a factor in your calculations. heat...

Kaylee Sepulveda 4G

This video is an introduction, and some of the following videos in the series describe the actual calculations more in-depth.

https://www.khanacademy.org/science/chemistry/acid-base-equilibrium/buffer-solutions/v/buffer-system

Kaylee Sepulveda 4G

This mainly depends on the substance that you add. For instance, an inert gas wouldn't affect the reaction at all. However, if you add something that reacts with either reactants or products, your system probably wouldn't remain at equilibrium because it would complicate the reaction and change the ...

Kaylee Sepulveda 4G

Gibbs free energy is a state function since it's defined in terms of thermodynamic properties that are also state functions. Hess's law can be used for both changes in entropy and in Gibbs free energy.

Kaylee Sepulveda 4G

C V is the molar specific heat at constant volume, and C P is the molar specific heat at constant pressure. So usually you will be told that a reaction is occurring at either constant pressure or constant volume, and you probably will be given the initial and final value if you are expected to use Δ...

Kaylee Sepulveda 4G

ΔS total =ΔS system +ΔS surrounding So if the ΔS total =0, then ΔS system = -ΔS surrounding They will not always be equal and opposite, but that is typically when this relationship will be important. Also, you could solve for ΔS system and ΔS surrounding and add if the question is asking for the ΔS ...

Kaylee Sepulveda 4G

Usually determining whether or not this is necessary will be a bit intuitive. In this particular problem, we were given a hint, but likely on an exam it will not be so obvious. Instead, take note of what information you are given and what you are being asked. For 12b, we were given the ΔH rxn = -275...

Kaylee Sepulveda 4G

Monatomic compounds are composed of single atoms, and diatomic compounds are composed of molecules containing two atoms. what-are-the-seven-diatomic-elements-606623-v3-5b562dab46e0fb0037fee8c7.png Difference-Between-Monatomic-and-Diatomic-Comparison-Summary.png I don't know why the C s values are 3/...

Kaylee Sepulveda 4G

Q is the amount of heat transferred to a system. ΔH is the change in enthalpy of a system in a reaction.

Q (heat) is not a state function. ΔH (change in enthalpy) is a state function.

Kaylee Sepulveda 4G

Positional entropy is the number of molecular positions or arrangements that a system can have. This relates to the "dog bones" that we went over in last week's lecture

Kaylee Sepulveda 4G

ΔH is the change in enthalpy and ΔU is the change in internal energy. Their relationship is explained by this equation: ΔH = ΔU + PΔV

Kaylee Sepulveda 4G

When a reaction is at constant pressure, the heat of reaction is equal to the enthalpy change of the system. Usually, you would be told there was a change in pressure, or it would be implied by the variables given.

Kaylee Sepulveda 4G

State functions are properties whose value does not depend on the path taken to reach that specific value. Some examples are internal energy, enthalpy, and entropy. However, things like heat and work aren't state functions, because they depend on the path taken from the initial to the final values. ...

Kaylee Sepulveda 4G

ΔH_sub=ΔH_fus+ΔH^vap

If we know the enthalpies of certain phase changes, we can calculate an unknown value using what is given to us.

Some helpful diagrams:

Kaylee Sepulveda 4G

The reason that the ΔH sublimation is equal to the ΔH fusion + ΔH vaporization is that sublimation is the transition from the solid phase to the gas phase without passing through an intermediate liquid phase. So, from this, we can infer that adding the ΔH of the transition from solid to liquid and t...

Kaylee Sepulveda 4G

Bond enthalpy is the energy needed to break a bond like C-H. Enthalpy of formation is the energy needed to form a substance from its pure components.

Kaylee Sepulveda 4G

A state property is a quantity that is independent of how the substance arrived at that state. Examples of state properties are altitude, pressure, volume, temperature and internal energy. A good way to imagine this is Dr. Lavelle's mountain example of the mountain, where one group takes a longer pa...

Kaylee Sepulveda 4G

Superheating and supercooling are very rare, as superheating is when something is heated past its boiling point without boiling/vaporizing. Similarly, supercooling is when an object is cooled below its freezing point without becoming a solid.

Kaylee Sepulveda 4G

The sodium oxide (Na₂O) is acting as a base, so sodium hydroxide (NaOH) is formed. It wouldn't form hydroxide and hydronium (H₃⁺ and OH^-)

Kaylee Sepulveda 4G

Here are some simple examples. Basically you have a acid or base in your reactants (remember, water can be both and is usually the second reactant) and the conjugate base is created by the acid donating a proton, and the conjugate acid is created by the base gains a proton. conjugate.png conjugate 2...

Kaylee Sepulveda 4G

Everything that we have covered so far is fair game, so I would not be surprised if at least one question required this formula. However, if I remember correctly, it is on the equation sheet.

Kaylee Sepulveda 4G

Since we figure out in part one that 10 -.75 =.018 mol⋅L -1 (.75 is the pOH and 10 -pOH undoes the log) we have to keep in mind that 5.00 mL of solution is added to the volumetric flask and diluted to 500.0 mL, so to find the molarity of the diluted solution in the second flask we have to take into ...

Kaylee Sepulveda 4G

This website explains everything step-by-step: https://courses.lumenlearning.com/cheminter/chapter/calculating-ph-of-salt-solutions/

Kaylee Sepulveda 4G

With the Ideal gas law, we assume things that we know are not true in a natural setting. For example, we'd ignore the volume that the ideal gas molecules would take up, and ignore intermolecular forces. However, outside of this idealized version of the situation, volume will be taken up by atoms and...

Kaylee Sepulveda 4G

There is actually a Khan Academy section that has some video lessons and practice problems related to Le Chatlier's Principle

https://www.khanacademy.org/science/chemistry/chemical-equilibrium/factors-that-affect-chemical-equilibrium/v/le-chatelier-s-principle

Kaylee Sepulveda 4G

Since K= [P]/[R], having a value of K>1 means that there is more product than reactant. Similarly, K<1 means there is more reactant than product. If K is small (K<10 -3 ) there are more reactants at equilibrium, and we would say that the equilibrium is "sitting to the left" If K is large (...

Kaylee Sepulveda 4G

n is the number of moles.

Kaylee Sepulveda 4G

In a sealed container, when a gas and its liquid form are at equilibrium, vapor pressure is the pressure of the gas above the liquid. Here is a video that explains it a bit more: https://www.khanacademy.org/science/chemistry/gases-and-kinetic-molecular-theory/ideal-gas-laws/v/vapor-pressure-example ...

Kaylee Sepulveda 4G

Here is a helpful diagram:

Kaylee Sepulveda 4G

Another thing to note is that cisplatin is effective and transplatin is not because a cisplatin molecule has chlorines on the same side, which can bond with two adjacent guanines. This creates a stronger hold, and prevents replication. Transplatin couldn't because the chlorines are on opposite sides...

Kaylee Sepulveda 4G

Hopefully this example will help: The boron atom in boron trifluoride, BF3, only has six valence electrons. Since it does not have a complete octet, BF3 is a Lewis acid and reacts with many Lewis bases. In this case, a fluoride ion acts as the Lewis base and donates one of its lone pairs. lewis acid...

Kaylee Sepulveda 4G

Anything given in lecture or written in the learning outcomes is "fair game", as Dr. Lavelle puts it. It would be beneficial to know the common formulas.

Kaylee Sepulveda 4G

The polydentate ligands form coordinate bonds with the central metal atom at multiple sites (implied by the number of the prefix) and monodentate would only form one coordinate bond

Kaylee Sepulveda 4G

A lewis acid accepts an electron pair, while a lewis base donates an electron pair.

Bronsted/Lowry acids donate a proton and the bronsted/lowry base accepts a proton.

Kaylee Sepulveda 4G

Kaylee Sepulveda 4G

Organic compounds always include carbon, while typically inorganic compounds do not. Also, most organic compounds contain C-H bonds. Keep in mind that simply containing carbon is not a sufficient explanation for a compound being organic. Molecules associated with living organisms are organic. These ...

Kaylee Sepulveda 4G

Crystal Field Theory is a model for the bonding interactions between transition metals and ligands. However, I'm fairly sure this topic is not in the Learning Outcomes Outline, so you shouldn't expect to encounter it on the final. I would definitely double-check on Lavelle's website if you're not su...

Kaylee Sepulveda 4G

Amphoteric compounds are molecules or ions that could react as either an acid or a base. Many metals like copper, zinc, tin, lead, aluminium, and beryllium form these amphoteric oxides or hydroxides.

A specific example of one would be Al₂O₃ (Aluminum Oxide), which is an amphoteric oxide.

Kaylee Sepulveda 4G

The coordination sphere is basically just the central atom/ion and the surrounding molecules or anions and ligands.

Usually if it's written out it will be within brackets

: coordination sphere.png (10.09 KiB) Viewed 161 times

Kaylee Sepulveda 4G

Oxoacids are acids that contain oxygen, another element, and have at least one hydrogen bonded to the oxygen. The acid strength increases when the central atom is unchanged and the amount of oxygens surrounding it increases. Also, with an unchanged amount of oxygen, the strength of the acid increase...

Kaylee Sepulveda 4G

Camille 4I wrote:Do lone pairs have more repulsion than double bonds?

Yes, the strength of repulsion goes
lone pair-lone pair > lone pair-bonding pair > bonding pair-bonding pair

Kaylee Sepulveda 4G

The VSEPR model is used to determine shape by taking into account the regions of electron density, and which regions will have stronger repulsions. This is why knowing the lone pairs is important. You can estimate the bond angles, but VSEPR is not 100% accurate so experimental observation is necessa...

Kaylee Sepulveda 4G

The groups of Electron Geometry are: Linear (2 regions e- density) linear.PNG Trigonal Planar (3 regions e- density) trigonal planar.PNG Tetrahedral (4 regions e- density) tetrahedral.PNG Trigonal-Bipyramidal (5 regions e- density) trigonal-bypyramidal.PNG and Octahedral (6 regions e- density) I co...

Kaylee Sepulveda 4G

The groups of Electron Geometry are: Linear (2 regions e- density) linear.PNG Trigonal Planar (3 regions e- density) trigonal planar.PNG Tetrahedral (4 regions e- density) tetrahedral.PNG Trigonal-Bipyramidal (5 regions e- density) trigonal-bypyramidal.PNG and Octahedral (6 regions e- density)

Kaylee Sepulveda 4G

Not all orbitals in a molecule become hybridized during bonding, however, when you are trying to figure out the hybridized orbital, you must take into account every region of electron density surrounding the atom. VSEPR is actually predicting these hybridized shapes, and then the hybridized orbitals...

Kaylee Sepulveda 4G

In terms of molecular shape, there would not be a difference because you'd have the same number of regions of electron density. Dr. Lavelle highlighted this in lecture when he was explaining why his non-ideal Lewis Structures were okay when doing VSEPR problems. However, if the question ever mention...

Kaylee Sepulveda 4G

The double and triple bonds are also treated as one region of electron density because, although they have more electrons that a lone pair or single bond, the electrons lie in the same region (between the two bonded atoms) and they are oriented in the same direction. This means that it is technicall...

Kaylee Sepulveda 4G

Only p orbitals can form π bonds and σ bonds are formed by the overlap of atomic orbitals over the internuclear axis. π bonds are oriented perpendicularly to the internuclear axis. S and P orbitals can form different hybridizations, s + p → sp s + p + p → sp² s + p + p + p → sp³ Overlapping hybridiz...

Kaylee Sepulveda 4G

Usually, the elements that do this are B, Al, Li, and H. B and Al will usually form compounds where they only have six electrons instead of a complete octet.

Kaylee Sepulveda 4G

It is possible that we will encounter common molecules and the formula will not be given.

Here is a helpful Quizlet to memorize them: https://quizlet.com/_3rd3b

Kaylee Sepulveda 4G

I believe the reason we covered the Schrödinger equation so briefly is that Dr. Lavelle doesn't really like this equation (I'm pretty sure one of the UA's said that) so we most likely won't encounter any problems where it will be necessary. Also, any equation we need will be given on the equation co...

Kaylee Sepulveda 4G

When I asked an undergraduate assistant about this, they said that typically the chemical formula would be given, and on the rare occasion you get a question where the name is given and the formula is not, it will either be a very common compound or it will be obvious from the name. For example, pho...

Kaylee Sepulveda 4G

They posted the answers on the original Dino Nugget thread but here

Kaylee Sepulveda 4G

Covalent character is referring to when an ionic bond takes on some covalent characteristics because electron distortion pulls electrons into the bonding area, so they are partially shared. I don't think we've discussed Fajan's rule yet but this explains the reasoning behind the phenomenon more (it ...

Kaylee Sepulveda 4G

Polarizability is referring to how easily displaced an atom's electrons are by neighboring atoms. In an ionic bond, ions which cause large distortions are referred to as having 'high polarizing power'. This distorts the electron density of an ion, so the electrons are being pulled into the bonding r...

Kaylee Sepulveda 4G

It's basically when the atoms in a molecule share electrons unequally.

μ = Q d
measured in debyes.

This video explains very nicely: https://www.youtube.com/watch?v=TyFd94TbdXU

Kaylee Sepulveda 4G

When referring to "most favorable", you want as many formal charges to = 0 as possible. Also, for instance, if you're drawing an ion with a net charge that is, for example, -1, your formal charges should add up to the net charge of the ion. Formal charges of 0 would indicate a more stable,...

Kaylee Sepulveda 4G

It's best to memorize exceptions to the rule because during the test you can use the rule to figure out every other answer. If we covered it in lecture, there is a good chance we will encounter it on a future test.

Kaylee Sepulveda 4G

Yes, you're on the right track

Kaylee Sepulveda 4G

I don't believe there is a particular formula for determining the number of resonance structures, so you would count the number of possible resonance structures by drawing every valid lewis structure until there aren't any possible alternative configurations.

Kaylee Sepulveda 4G

You can estimate bond lengths by adding the covalent radii of the two atoms, but this is not entirely accurate and experimental observation is always the better option.

Kaylee Sepulveda 4G

This video explains the idea very simply: https://www.youtube.com/watch?v=cIuXl7o6mAw

Kaylee Sepulveda 4G

Does this image help?

Kaylee Sepulveda 4G

A nodal plane is a plane where the probability of finding an electron is zero. You can find the coordinates of these planes by solving the Schrödinger wave equation

Kaylee Sepulveda 4G

The value of the energy level is proportional to 1/n^2 which gives a series 1, 1/4, 1/9, 1/16, and so on

Kaylee Sepulveda 4G

Here is a quick video that explains it:
https://youtu.be/XK-WTYncldA

Kaylee Sepulveda 4G

You find the Energy per photon with E = hc/λ, and divide the 64J by the energy per photon to find out the number of photons, then you can multiply by Planck's constant to find the mols of photons

Kaylee Sepulveda 4G

The mass of a neutron is 1.6749286*10^-27 kg

Kaylee Sepulveda 4G

Crash Course Part 1 [youtube]https://www.youtube.com/watch?v=7kb1VT0J3DE[/youtube]

Crash Course Part 2 [youtube]https://www.youtube.com/watch?v=qO_W70VegbQ[/youtube]

Introduction (pretty boring but covers basic concepts) [youtube]https://www.youtube.com/watch?v=HC81oYe43DI[/youtube]

Kaylee Sepulveda 4G

Electrons aren't emitted unless the energy of the photon is greater than or equal to the energy to remove an electron, even for high-intensity light. This outcome was unexpected, because the light was no longer behaving like a wave, otherwise simply raising the intensity would have been sufficient t...

Kaylee Sepulveda 4G

Intensity is proportional to the square of amplitude. So, as a general rule, as the amplitude of a wave increases, so will the intensity.

Kaylee Sepulveda 4G

To keep your work as accurate as possible, try not to round until the final answer. On the basis that you do round, keeping a certain number of significant figures should be enough to result in the final answer. For example, if the answer needs to have two significant figures, keeping four signific...

Kaylee Sepulveda 4G

Do we have to sign up for your workshops or are students welcome to just show up?

Kaylee Sepulveda 4G

Before the test, you definitely want to make sure you are in the right head space. If you know you have an exam coming up, make an effort to get sleep and eat a good breakfast. Give yourself adequate time to study in advance so you do not feel like you are cramming the night before. Some light revie...

Kaylee Sepulveda 4G

I'm a bit rusty on sig figs since I haven't taken chem in a few years, does anybody have any specific resources for practicing that they found helpful? I learn better from practicing than memorizing rules and definitions.

Kaylee Sepulveda 4G

Do you have any advice for professors who are not as accommodating as Lavelle? Did you ever struggle in a specific class because of a lack of resources/support?

Kaylee Sepulveda 4G

Its been a while for me too! I know this is basic, but knowing the common ions and compounds is so important to setting up problems and writing equations, but our course reader doesn't include much about them. I have this review list that will totally help!Common Ions.docx Thank you, I have been st...

Kaylee Sepulveda 4G

Thank you for sharing your experience. I am planning to go to medical school, and it is comforting to hear from people who have been in my situation and are doing well.

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