CHEMISTRY COMMUNITY

Dominic Benna 2E

The frequency factor, or A, is the fraction of collisions between molecules that will have the correct orientation in order to form products. Some reactants require that there be a certain orientation during the collision between them in order to form products, and the frequency factor is used to in...

Dominic Benna 2E

Rates are dependent on the amount of reactant. As a reaction goes forward, the amount of reactant falls as it becomes product, and thus the rate of the reaction changes as there are less reactants and products start to form reactants in the reverse direction. By taking the initial values, or the max...

Dominic Benna 2E

The prime next to the k does not denote the derivative of k. It is used to symbolize the reverse rate of a reaction. However, I believe I have also seen it to differentiate between two rate constants for two equations.

Dominic Benna 2E

Zero-order reactants mean that they do not depend on the amount of the reactants, only on the rate of k, which in this case would be a -k.

Dominic Benna 2E

The overall reaction order can be zero if all reactants are zero-order. This would mean that the rate of the reaction would just be based on the constant, and not the initial values of the reactants.

Dominic Benna 2E

A compound cannot be oxidizing and reducing at the same time. This confusion may come from the fact that a compound that is oxidized is the reducing agent and a compound that is reduced is the oxidizing agent.

Dominic Benna 2E

qrev is the amount of heat that can be produced (or lost) in a reversible process. So it is saying in this equation it is not asking for the heat produced or lost by an irreversible reaction.

Dominic Benna 2E

Even when a system cannot exchange energy or substances with the surroundings it can still have internal changes. For example a bomb calorimeter can have a reaction within it that changes the two substances or two substances can be in an isolated system at different temperatures and exchange energy ...

Dominic Benna 2E

For this class they are the same for calculations.

Dominic Benna 2E

Definitely quantum

Dominic Benna 2E

A spontaneous reaction has a positive delta E, yet a negative delta G. So, in order to relate the two to each other, the negative sign is added.

Dominic Benna 2E

Leo is just a term to help you understand oxidation and a way remember the difference between oxidation and reduction. LEO stands for "Loss of Electrons: Oxidation". It reminds you what oxidation is, when electrons are lost, as well as reminds you that oxidation is when electrons are lost,...

Dominic Benna 2E

Yes, you can. In a reduction, the electrons are gained, thus they would be on the reactants side. In oxidation, electrons are released, thus they would be on the products.

Dominic Benna 2E

State functions are independent of the path taken, so their values are only dependent on the starting and ending values.

Dominic Benna 2E

That just means that no heat transfer occurs between the surrounding and the system.

Dominic Benna 2E

As degeneracy increases so does entropy because as the amount of possible states increase, so does the randomness possible from it.

Dominic Benna 2E

It is always positive for a spontaneous reaction.

Dominic Benna 2E

Delta G naught is at standard conditions. You will know to use this in your equation if they give the standard condition values or say that the system is under standard conditions.

Dominic Benna 2E

Delta U = q+w
but at constant pressure, q=delta H
so delta u at constant pressure = delta H + w

Dominic Benna 2E

Reversible work is work done is infinitesimally small steps, or changes, so if the pressures are the same to start yet slowly change it is reversible. The second equation you wrote out is for reversible work. Irreversible work can be identified by one large step and large differences in pressure bet...

Dominic Benna 2E

Lavelle has used just celsius + 273 to get the conversion to Kelvin, so I believe that will work most of the time. I believe, however, that the exact number to use is 273.15.

Dominic Benna 2E

Positive work is work that is done on the system, as it is gaining energy. Negative work is work done by the system, as it is losing energy.

Dominic Benna 2E

The integral for the work equation for a reversible reaction is not technically needed to solve the equation. It is shown to explain how we got it and why we use it, yet by simplification, the actual integral is not needed. The Ln of the two volumes works too.

Dominic Benna 2E

If the work is done on the system, it is gaining energy so the value should be positive. If the system is doing the work, then it is negative since it is losing energy.

Dominic Benna 2E

Reversible reactions have infinitely small changes applied to it, take much longer, and produce far more work done. Irreversible reactions involve one step, have a high pressure difference, and produce less work done.

Dominic Benna 2E

The V1 and the V2 are the initial and final volumes of the system. The way I remember this is the bottom number on the integral is the lower bound and the top number is the upper bound of the integral.

Dominic Benna 2E

Heat capacities cannot be negative, because it is the measurement of heat supplied to something. It is the amount of heat to raise it's temperature, so it must be positive.

Dominic Benna 2E

If a system is isochoric, isotermal, and isobaric, does that automatically make it an isolated system?

Dominic Benna 2E

The difference between isochoric and isometric is in their definition. Isochoric means there is no change in volume or that it has a constant volume. Isometric, on the other hand means that it has the same dimensions. I believe both terms can be used interchangeably.

Dominic Benna 2E

I believe that Lavelle explained that the difference between reversible and irreversible pathways is the magnitude of the change of the system, which depends on the if the system is at equilibrium or not. When the system is at equilibrium, an irreversible pathway is possible by slightly changing the...

Dominic Benna 2E

If there is a large pressure difference between the system and the surrounding, like the piston, why is the system not able to be reversed?

Dominic Benna 2E

The pressure is constant because there is no within the system, including the change in pressure.

Dominic Benna 2E

Extensive properties depend on the amount being measure, yet intensive do not. For example, mass is extensive and density is intensive.

Dominic Benna 2E

All thermodynamic equations should work because open systems deal with matter and heat.

Dominic Benna 2E

Will we be working with isolated systems mathematically if there is no change in energy?

Dominic Benna 2E

State properties only take into account final values, not the path taken. Enthalpy is a state property. Since sublimation is the transition from solid to vapor, then that must equal fusion(solid to liquid) plus vaporization(liquid to vapor) of the same material.

Dominic Benna 2E

The reason why it's temperature doesn't increase is because the energy that is being given to the system is being used break bonds for the phase change to happen.

Dominic Benna 2E

Ka and Kb are both found by using [P]/[R]. The difference between the two is that Ka is used for acids and Kb is used for bases.

Dominic Benna 2E

How do you find out how a reaction will react to a change in partial pressure of either its reactants or products?

Dominic Benna 2E

Work (w) and heat (q) are both dependent on the paths they taken. This means that their quantities are based on the past and not just their current quality. This means that they are both not state variables.

Dominic Benna 2E

[H2O] is left out because it is found in large amounts on both the product and reactant side of the equation. This means, when calculating for Kw, the amounts of [H20] would just cancel each other out.

Dominic Benna 2E

Strong acids do have a lower pH than weaker acids, but I am guessing that it was due to the concentration of the weak acid in those questions that caused the pH to drop so much. 0.001M of a strong acid will completely dissociate, but only create 0.001M of H3O+, but 0.1M of a week acid could create m...

Dominic Benna 2E

Yes. Kw will always be equal to 10^-14, so if you have either the Kb or Ka values, you can find the other easily!

Dominic Benna 2E

I am having a hard time with this one question on the week two sapling homework. I believe that I am getting the right concentration for [OH-] and plugging in the right numbers into the Kb equation to find the concentration of [B], but my percent pronated number just doesn't make sense, as it is abo...

Dominic Benna 2E

I think ICE boxes are especially helpful to use when working with weak acids and bases. However, I think it is just good practice to also use them with strong acids and bases, however, I do not think it is necessary.

Dominic Benna 2E

How do I know how K will be affected based on a change in temperature? Does is depend on if the reaction is endothermic or exothermic?

Dominic Benna 2E

You would use partial pressure when finding Kp or are only dealing with gases in the equation. If the reactants and products are not all gases or are asked for Kc, then you would use concentration.

Dominic Benna 2E

Kc is always used when you are given the molar concentrations or the moles of the products or reactants. Kp is used when you have only gases, or if, in the equation, it mentions atm/bar for the units.

Dominic Benna 2E

Only Q would change, so you would only need to find the value of Q in that situation. The only time that K changes is if the temperature changes, not if the amount of reactants or products changes.

Dominic Benna 2E

It basically depends of the units in the equation. However, I think Lavelle said that we would be using atm mostly, so the most likely value you would be using for R would be 8.206 x 10^-2.

Dominic Benna 2E

Will we have to identify if an acid or base is strong or weak based off of pH? If so, what is the pH range for a strong acid verses weak acids, and the same for bases.

Dominic Benna 2E

You find the oxidation number of the metal by looking at the overall charge of the coordination compound and the individual charges of the ligand and atoms within the compound. You use the metal to balance the charges within the coordination compound to match the overall charge of the compound.

Dominic Benna 2E

When the hydrogen breaks from the H20 to the O2-, the H20 becomes one of the OH- and the O2- that gained an H becomes OH- too. That is why you get two moles of OH- for every mole of O2-.

Dominic Benna 2E

The H in the COOH of the CH3COOH breaks off as a positive proton, so it makes it an acid.

Dominic Benna 2E

What equation should I use to convert a pOH- value into a [H+] value in molarity?

Dominic Benna 2E

Yes it is. The reasoning behind it being stronger is that the anion created from trichloroacetic is more stable than acetic acid. This is due to the Cl's delocalizing the negative charge of the oxygen and the resonance structure that is created when the H is broken off.

Dominic Benna 2E

No because there will be theoretically a 100% dissociation of the acid or base.

Dominic Benna 2E

H20 should be labeled a liquid because it is the solvent of the aqueous solution. An aqueous solution is created when water is the solvent, so H20 by itself wouldn't be aqueous.

Dominic Benna 2E

I believe that we just need to know relatively their pH. For example that vinegar is acidic and bleach is basic. I don't think we have to know their exact values however.

Dominic Benna 2E

The difference between organic and inorganic bases is that an organic base contains carbon atoms where inorganic bases don't.

Dominic Benna 2E

Are coordinate compounds only possible with a transition metal cation? Or can any ionic compound be a coordinate compound?

Dominic Benna 2E

What is a delocalized pi bond? How are you able to recognize and point out what is a delocalized pi bond?

Dominic Benna 2E

The position of the atoms determines its shape, and lone pairs influence where the position of the atoms will be. It he were to ask for the electron configuration, lone pairs would be taken into consideration when determining the shape; however, for finding the shape of a molecule, the positions of ...

Dominic Benna 2E

First, you would want to count the lone pairs and the bonds. Since this one has 4, it would be sp^3. One orbital from the s-orbital and 3 from the p-orbital.

Dominic Benna 2E

When there is a double bond is involved, does that count towards the hybridization of an atom? Would a central atom with two single bonds and a double bond be sp^3 or sp^3d?

Dominic Benna 2E

What is the difference between a Dipole-Dipole interaction and a Dipole-Induced-Dipole interation?

Would their relative strengths be different too?

Dominic Benna 2E

A triple bond has 1 sigma and 2 pi

Dominic Benna 2E

Florine is extremely electronegative. This means that this molecule will be polar, and because it has a hydrogen, it can form a hydrogen bond. For reference, O, N, and, F are the three atoms that, when bonded to a hydrogen, can form hydrogen bonds.

Dominic Benna 2E

It increases as you go right across a period, and it decreases as you go down a group. So, Florine, for example, is the most electronegative atom.

Dominic Benna 2E

Carbon and hydrogen have a very similar electronegativity. That is why when they show a chart of the electronegativity of atoms they place hydrogen above carbon. But yes, looking straight off a periodic table it is not noticeable.

Dominic Benna 2E

See how many electron pairs connected to either a N,O, or F atom and each one can pair with one water molecule.

Dominic Benna 2E

From what Professor Lavelle said in lecture, they generally have the same force.

Dominic Benna 2E

It is not so much that the electrons are shared. Instead it is the attraction between the partially positive charge of the hydrogen and the partially negative charge of the other atom that created the hydrogen bond.

Dominic Benna 2E

You can tell if there is an odd number of valance electrons or on the diagram there is a lone electron.

Dominic Benna 2E

The formal charge on carbon would be -2, not -1

Dominic Benna 2E

A coordinate covalent bond is when the two electrons that form a covalent bond come from the same atom, rather than one electron from each.

Dominic Benna 2E

Press the more option on the top of that window. From there you should be able to choose either a positive or negative charge to add to the atoms.

Dominic Benna 2E

Those are the exceptions because they will not get up to 8 valence electrons. They will either gain electrons to gain a full shell of two electrons or lose a certain number of electrons to have a full shell of two valence electrons.

Dominic Benna 2E

They are the exceptions to the octet rule because they can have d-oribitals.

Dominic Benna 2E

It is more distorted because the electrons are being shared more. When the bond is more covalent, that means that the electrons are being shared more. Then there will be a distortion between the two atoms.

Dominic Benna 2E

noelle_lipschutz_3F wrote:Can someone explain how to use the periodic table to determine electron affinity?

I believe that affinity increases as you go right down a period it increases and decreases as you go down a row!

Dominic Benna 2E

So why is the 2nd ionization energy so much higher than the first ionization energy for atoms?

Dominic Benna 2E

You can't find the radius of an atom off of a singular atom, but you can find the radius of a single atom be finding the distance between two nuclei and dividing by two.

Dominic Benna 2E

a) would be the right answer because there are only s and p orbitals in the second energy level

Dominic Benna 2E

If an electron spin state is +1/2, it means the electron is spinning upwards/clockwise on its axis. If the spin state is -1/2, the electron is spinning downwards/counterclockwise on its axis. I know that is what it says in the book and the diagrams Lavelle showed us, but what exactly does it mean b...

Dominic Benna 2E

For the second part of #19 on the sapling homework, I keep getting 5.67x10^-2 m/s, but it says that it is incorrect.

This is the question for reference:
What is the minimum uncertainty in a helium atom's velocity if the position is known to be 1.4 angstroms

Dominic Benna 2E

Thank you!

Dominic Benna 2E

Will there be questions on the midterm where we will have to choose between two answers with differing sig figs?

Dominic Benna 2E

Will we have to know how to convert between kg to g or km to m for the midterm?

Dominic Benna 2E

Hey guys,
I have been working on this problem but I can't seem to get it right. Thought you guys could help me with the steps.

A bowling ball of mass 8.00kg is rolled down a bowling alley lane at 5.00 +/- 5.0 ms-1. What is the minimum uncertainty in its position?

Dominic Benna 2E

I have been having some trouble trying to find the n-levels that an electron will be excited or dropped to based on a given wavelength. For example: In the ultraviolet spectrum of atomic hydrogen, a line is observed at 102.6nm. Determine the values for n for the initial and final energy levels of th...

Dominic Benna 2E

Ryan_Kien_1L wrote:Review sessions happen every week. The schedule is posted here: https://lavelle.chem.ucla.edu/wp-conten ... PL_ALL.pdf

Thank you!

Dominic Benna 2E

I will be reviewing the modules, but I think that the best way to study for the midterm would be to do the practice problems Lavelle assigned in the textbook. But that's just my opinion!

Dominic Benna 2E

Didn't Lavelle also say that we didn't necessarily need to know about Black Bodies for the course?

Dominic Benna 2E

Hi! I believe you would approach the problem E = hv and c = λv. You're given E, and if you rearrange the E = hv equation, you get v = E/h. When you plug that into the c = λv equation, you'll get c = λ(E/h). Multiply both sides by h, divide both sides by E, and then solve for λ. Hope this helps That...

Dominic Benna 2E

What is HIJKLMNO?

H2O

Dominic Benna 2E

Dominic Benna 2E

First, you would need to plug this number into the E = hV equation as your E. From there you get your frequency. Then you plug that into the c= λV equation to get your wavelength.

Dominic Benna 2E

The + - 10 just symbolizes that the amount could vary anywhere between 90-110 g/mol.

Dominic Benna 2E

A trailing zero without a decimal point does not make the number more precise, so they do not count as sig figs. The zeros are just place holders to show the true value of the number.

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