CHEMISTRY COMMUNITY

Max Hayama 4K

I believe Professor Lavelle mentioned that the frequency factor is the percent of successful collisions. So if 10% of collisions are successful based off orientation, the frequency factor, A, will be .10.

Max Hayama 4K

I believe it is possible to have many fast steps before the slow step, as long as there is a fast step preceding the slow step, which will result in the accumulation of product during this fast step and create equilibrium.

Max Hayama 4K

I believe the units for the rate constant will depend on the order of the reaction. For example, if the reaction is first order, the units for k will be 1/s.

Max Hayama 4K

Aqueous solutions of (a)Mn+2, (b)Al+3, (c)Ni+2, (d)Au+3 with concentrations of 1M are electrolyzed at pH=7. For each solution, determine whether the metal ion or water will be reduced at the cathode. The solutions manual says that the species with the most positive E value will be reduced at the cat...

Max Hayama 4K

Given that we have the initial concentration of A, or [A]o, [A] is the concentration of A after some time, t.

Max Hayama 4K

I believe for the purposes of this class, only 0, 1st, and 2nd order reactions will be tested.

Max Hayama 4K

To add to the previous comment, I believe the rate at which C is formed will be 3/2 the rate at which A is decreasing, because 3 C's will form for every 2 A's being used up!

Max Hayama 4K

I believe they are interchangeable. As long as they are on the correct side of the salt bridge, it should be fine.

Max Hayama 4K

In this equation, n is the moles of electrons transferred within the redox reaction.

Max Hayama 4K

Because temperature is measured in Kelvin, it is not possible to have a value below 0, since we call the lowest possible temperature absolute 0. Therefore, if deltaH is negative and deltaS is positive, it will not matter what temperature the reaction is at. It will always be spontaneous.

Max Hayama 4K

By using the deltaH, deltaS, and T, we can find the value of delta G using the equation (deltaG= deltaH- T*deltaS)

Max Hayama 4K

Normally a negative deltaH indicates spontaneity assuming that delta S is positive or that the temperature of the reaction is low. This will result in a negative deltaG value most of the time.

Max Hayama 4K

Why is it that if deltaS total is positive we can immediately assume the reaction is spontaneous? I understand that if just deltaS is positive, its difficult to determine whether or not the reaction will be spontaneous. But if deltaS total is positive we can immediately assume the reaction is sponta...

Max Hayama 4K

I came across this problem too. I think if it's not specified what kind of ideal gas it is, you can use the equation in the solutions manual.

Max Hayama 4K

When is it safe to assume that delta S is equal to 0? Under what conditions and how does this impact S of surroundings and system?

Max Hayama 4K

You should only be worried about what Ka value is associated with a weak acid, since this will determine whether or not you can make assumptions. However for the midterm, Dr. Lavelle said there would be no questions in which you can make the assumption that x is essentially insignificant.

Max Hayama 4K

Can anyone explain why we raised 2^avogadro's number during lecture? I didn't understand what this had to do with degeneracy/entropy.

Max Hayama 4K

Because the system is not doing any work against the surroundings to change the volume (or vise versa), it is safe to assume that under constant volume that no work is being done by or on the system.

Max Hayama 4K

Think of residual entropy as something that is completely unmoving, something without thermal energy, rotational motion, or translational motion.

Max Hayama 4K

Can anyone explain the reason behind the negative or positive sign when calculation delta H? I understand it's negative because it exothermic and vise versa, but I was confused when Professor Lavelle discussed the qsystem and q surrounding.

Max Hayama 4K

Because most calorimeters have insulating properties that allow for the heat of the reaction to not disperse outside of the container. This allows for more accurate results and less experimental error.

Max Hayama 4K

The reason why O2 has a standard enthalpy of formation of 0 is because diatomic oxygen is the most stable in this form, therefore it requires no change to achieve this state!

Max Hayama 4K

If the concentration of OH- or H+ is less than 1e^-7, which are the standard concentration for autoprotolysis of water, then you can assume that the pH of the solution is neutral or at 7. This is because naturally there exists a concentration of either OH- or H+, so any value that is less than 1e^-7...

Max Hayama 4K

Usually a salt will include the conjugate acid/base of the acid/base that is ionizing. For example the weak acid, NH3, and its salt, NH4Cl, will form a buffer solution.

Max Hayama 4K

Kw will be 10^-14 only if the temperature is 25 degrees Celsius. If the temperature is different, the equilibrium constant for the autoprotolysis of water will also be different. This is because autoionization is endothermic, meaning an increase in temperature will result in more products, shifting ...

Max Hayama 4K

If the question gives you partial pressures, normally in atm, then you will be calculating for Kp. If you are given the concentrations of the reactants or products then you will most likely be calculating for Kc. Of course, make sure to determine what the question is asking for.

Max Hayama 4K

Yes! All you need to do is divide the equilibrium concentration of the conjugate acid/base by the initial concentration of the corresponding acid and base.

Max Hayama 4K

I believe this is correct! If the conjugate acid has a high pKa, the Ka value is small, meaning the ability to donate a proton is not strong. Therefore the ability for the conjugate acid to form the base is also small, meaning the base is strong.

Max Hayama 4K

When calculating for equilibrium concentrations using initial concentrations, the variable "x" is used as a placeholder for the change in concentration from initial to final. When is this change negligible enough to disregard it, so that solving quadratic or cubic equations can be made sim...

Max Hayama 4K

I believe (a) is true because once a reaction reaches equilibrium, the amount of products and reactants will stay the same. Therefore, this ratio of products to reactants will be unchanged unless the temperature changes. (b) is most likely false because the rate at which the reaction occurs has no i...

Max Hayama 4K

Catalysts have no impact on the equilibrium constant or favor a specific direction of the reaction (forward or reverse). It does however increase the reaction rate which will be discussed later.

Max Hayama 4K

I believe Bronsted is more general, since it refers to being an electron pair donor or acceptor, while Lewis regards being a proton acceptor or donor, which some acids and bases may not have.

Max Hayama 4K

I don't think it is ignored, but in the case of CH4, there is no dipole moment because the tetrahedral structure will cancel out the dipoles, therefore making it nonpolar.

Max Hayama 4K

I believe polyprotic acids, after giving off a hydrogen ion, can be amphoteric since it isn't as strong as originally and the reverse reaction is favored. Therefore it acts as slightly acidic while also slightly basic since the reverse reaction is possible, as well as the next forward reaction.

Max Hayama 4K

Because the number of orbitals are conserved, this means that the amount of atomic orbitals we begin with will be equivalent to the number of hybrid orbitals we end with.

Max Hayama 4K

Yes, the higher attractions between molecules due to intermolecular forces, the higher the melting and boiling points will be!

Max Hayama 4K

Does anyone know why the chlorines unbind from the ligand, and not the amine groups? Shouldn't the bond between platinum and ammonia be more prone to breaking off as opposed to the chlorine?

Max Hayama 4K

You could say that the speed of the ejected electron and the frequency of the incoming radiation are directly proportional, because if frequency increases, the energy of the incoming photon also increases. Thus, this will increase the kinetic energy of the electron due to the law of conservation of ...

Max Hayama 4K

Ge has 4 valence electrons, and there are four fluorines surrounding it. Therefore you can assume that it will form 4 single bonds with each fluorine. Just to be safe, you can count the amount of valence electrons for all the atoms, which is 32, and subtract 8 from the 4 single bonds. You're left wi...

Max Hayama 4K

Can anyone explain why sp^3d^2 exists? Why is it that the d orbital is involved in hybridization?

Max Hayama 4K

Why is it that lone pair repulsion is greater than bonding pair repulsion?

Max Hayama 4K

Because Mg is smaller than Ba, it will exhibit some covalent character since the nucleus will slightly pull on the electrons around the oxygen. Therefore BaO has more ionic character than MgO.

Max Hayama 4K

Although fluorine has a larger electronegativity than iodine, there is still a covalent bond between the carbon and the fluorine so their is no permanent dipole between the two. As a result, iodine has a lot more electrons than fluorine, making it more polarizable thus resulting in greater induced d...

Max Hayama 4K

The polarizability of electrons in a molecule will impact the electron distortion. These electron distortions create dispersion forces that will impact the intermolecular forces acting between molecules. As a result, if there are greater intermolecular forces amongst molecules, it will require more ...

Max Hayama 4K

When drawing your Lewis structures, make sure to accommodate an octet for any element in period 2, while any element in period 3 and above can have an expanded octet. This depends on the formal charge of the central atom and the surrounding atoms to ensure that the lowest energy state is achieved.

Max Hayama 4K

All atoms have fluctuating electron distributions that will be distorted in some way, which will create an induced dipole. These forces are more prevalent in atoms with more electrons compared to atoms with less electrons, because there are more electrons that can be polarized.

Max Hayama 4K

O3 has both a double and single bond in it's most stable, lowest energy Lewis structure. We were taught that in reality, these bonds would be an average between a double and single bond. So when asked whether ozone has one or two different bonds, would we say that it has one type of bond? Or would w...

Max Hayama 4K

What causes the formation of radicals? If they are in a more stable state prior to being a radical, why are they left with 7 valence electrons?

Max Hayama 4K

We will not be expected to memorize ionization energies of different elements. As long as you know the general periodic trends, you should be fine!

Max Hayama 4K

Typically, a chemical formula is used to represent a singular atom, whereas a molecular formula is two or more atoms bound together. Also, bismuth(iii) fluoride is technically the same as bismuth trifluoride, but since it's an ionic compound, bismuth(iii) fluoride is the right way of naming the comp...

Max Hayama 4K

Which elements are predicted to have the following ground state electron configurations of their atoms?
(d) [Rn] 7s^2 6d^2

Answer in the solutions manual is Thorium, which is in the 5f subshell. Why is it not rutherfordium? Which is in the 6d subshell.

Max Hayama 4K

Because they all reside in the same row, all of the valence electrons will experience the same shielding. The only difference is the number of protons, which will pull the electrons inwards, thus decreasing atomic radius. As a result, chlorine has more protons than sulfur and phosphorus, so it has t...

Max Hayama 4K

Arrow down does not necessarily represent an excited state, it only indicates that an electron has a spin opposite to arrow up. However, if the other electrons in the subshell have arrows upward and one is down, this signifies an excited state because the most stable/conventional spins for a half fi...

Max Hayama 4K

Jessica Dharmawan 1G wrote:Do we have to memorize these for the test this week?

I think it would be a good idea to familiarize yourself with these series, since they might throw it in the test. Just remember Lyman series has an final state of n=1, Balmer is n=2, and Paschen is n=3.

Max Hayama 4K

During lecture, a visual was shown displaying how an electron as a wave would look. What happens when there are two electrons? Will the waves look different?

Max Hayama 4K

To start off, we need to find dp because momentum will allow us to find velocity. Therefore, you divide planck's constant by (4pi * dx), dx being the uncertainty of distance which is 10. Doing this will give you 5e-36 kg*m*s-1, our uncertainty in momentum, and using p=mv, you divide momentum by the ...

Max Hayama 4K

If delta v signifies a range of possible velocities of an electron, isn't it possible that the velocity could be less than the speed of light? How do we know that the velocity of the electron is more than the speed of light if the range doesn't specify whether of not it is?

Max Hayama 4K

I think you mistakenly used BrF3 as the limiting reactant, when ClO2 should have been used to determine how much product is produced. In other words, 5 mols of BrF3 will result in 2.5 reactions when 12 mols of ClO2 will result in 2 reactions. Therefore, we use the mols of ClO2 as our limiting reacta...

Max Hayama 4K

It was mentioned in lecture that if the energy of the incoming light is equal to the amount of energy needed to remove an electron from a metal's surface, then the kinetic energy of the removed electron would equal 0. This means that the electron would only move(be detected) due to the charge differ...

Max Hayama 4K

The unit eV stands for electron volt, and is approximately 1.602x10^19 J per 1 eV. Therefore, to begin this problem, you should convert 140.511 KeV to eV by multiplying by 1000, then multiply that by 1.602x10^19 to get the joules. Then use the energy equation to find frequency, and use this frequenc...

Max Hayama 4K

Silver will normally occupy an oxidation state of +1; it is just a common known transition metal oxidation number that is handy to memorize. Other honorable mentions include aluminum, which has an oxidation number of +3, and zinc, which has an oxidation number of +2.

Max Hayama 4K

I am also getting 4.57x10^-2 as my answer for part A. Could just be a simple rounding error, because the amount of moles of K+ should be .02285, but the book rounds it to .0229 before dividing by volume.

Max Hayama 4K

A student prepared a solution of sodium carbonate by adding 2.111g of the solid to a 250.0mL volumetric flask and adding water to the mark. Some of this solution was transferred to a buret. What volume of solution should the student transfer into a flask to obtain (a) 2.15 mmol Na+ (b) 4.98 mmol CO3...

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