CHEMISTRY COMMUNITY

Brandon Mo 4K

Will we be required to use the steady-state approach or do we only need to know how to use the pre-equilibrium approach?

Brandon Mo 4K

Using the integrated rate law of the first order reactions: ln [A] = -k t + ln [A]o, you can solve for the half-life (t1/2) by setting [A]= (1/2)[A]o.

Eventually you get, t1/2 = ln(2)/k or 0.693/k.

Brandon Mo 4K

Intermediates are the things that are produced in one step but used up in a later step. They do not appear in the overall chemical equation. These are the ones that are canceled out when you add the steps together and they are not reactants present in beginning.

Brandon Mo 4K

You can find the unique rate expression of the each reactant and product, then set it equal to the unique rate.

For example:
(-1/3)(d[O2]/dt) = -(0.44 mol/Ls)

Brandon Mo 4K

I think the rate of consumption is the rate that the reactants are being used up. The rate of formation is the rate that the products are being formed.

During that problem, I think you are supposed to interpret the reaction rate as a unique rate to find the rate of consumption/formation.

Brandon Mo 4K

What does the order of each individual reactant mean? What does the overall order for the reaction mean?

Brandon Mo 4K

What is the difference between being kinetically stable and thermodynamically stable?

Brandon Mo 4K

When K<1, there is a higher concentration of reactants than products. This indicates that products are not being favored in equilibrium. This would lead to how delta G would be positive, or nonspontaneous. You can also look at the equation delta G = -RTln(K). Having a K<1 would result in a negative ...

Brandon Mo 4K

You are able to find n by creating the half reactions and balancing them so the number of electrons are equal. The number of electrons being transferred would then be the number of electrons you have found to balance the half reactions.

Brandon Mo 4K

What exactly is a standard hydrogen electrode and what do we need to know about it?

Brandon Mo 4K

How do we determine the number of electrons in the oxidation and reduction half-reactions?

Brandon Mo 4K

When is a reaction spontaneous in terms of Gibbs Free Energy, enthalpy, and entropy?

What does being spontaneous actually mean?

Brandon Mo 4K

The temperature would be given in the problem. To find delta n, you balance the chemical equation and take the difference of moles of gas between the products and reactants.

Brandon Mo 4K

We only consider the moles of gases. You can ignore the other things.

Brandon Mo 4K

How do we compare the standard entropies between complex molecules?

What are the general rules used?

Brandon Mo 4K

How are we supposed to calculate W (degeneracy)?

Brandon Mo 4K

Could someone explain the derivation of work of reversible expansion? Also, what is the difference between reversible work and irreversible?

Brandon Mo 4K

How do we tell which heat capacity to use (heat capacity, specific heat capacity, and molar heat capacity)?

Does anyone also know the variables used for them?
In my notes there are C, Cv, Cp, Csp. I am confused which one is which.

Brandon Mo 4K

How do we find the degeneracy of something? I am confused on how we are supposed to use the equation.

Brandon Mo 4K

The sealed beaker is a closed system because it can still exchange energy with surroundings. It cannot exchange matter with its surroundings because it is sealed with a fixed volume. However, energy can transfer because it is not insulated, meaning heat can be exchanged. It's like when a sealed cup ...

Brandon Mo 4K

Don't forget that you can also check the constants and equations sheet on the class website. Everything on it will be provided during exams.

Brandon Mo 4K

Steam causes severe burns because it releases a lot of energy very quickly when it turns back into liquid water.

Brandon Mo 4K

The standard enthalpy of formation is the standard reaction enthalpy for one mole of a substance from its elements that are in their most stable form. For example. O2 --> O2 The standard enthalpy of formation for O2 is zero because it is already its most stable form so there is no change in enthalpy.

Brandon Mo 4K

Could someone explain why using enthalpies is the least accurate method? Does this mean that we should try to always use the other two methods instead?

Brandon Mo 4K

I don’t think you have to convert to bars. I think it’s recommend to stick with the units that are given in the questions.

Brandon Mo 4K

You usually know when they ask for Kp (partial pressure) or Kc (molarity). You can also convert between the two by using the ideal gas law PV = nRT.

Brandon Mo 4K

You should not round until the end of calculations. Try to keep the as many digits as possible when doing calculations or save them in your calculator. But you do have to keep track of the significant figures during calculations.

Brandon Mo 4K

You can also tell if x is negligible by seeing if the value of x is less than 5% of the initial molarity of the reactant after using the approximation.

Brandon Mo 4K

Are there ever any instances where the initial concentrations of the products are not 0?

In the answer key of 12.79 (6th Edition), why is it that the initial molarity of H30+ is not 0?

Brandon Mo 4K

Why does adding inert gas to a container have no effect in reactant, product concentration, and the reaction?

Does this apply to only inert gases? What happens if you add other gases?

Brandon Mo 4K

When a reaction reaches equilibrium, the forward and reverse reactions continue to proceed while the concentrations of reactants and products do not change.

Brandon Mo 4K

How are we supposed to use Q to determine whether a system is at equilibrium?

Brandon Mo 4K

Why is it that when we know the Kc of the forward reaction, we also know the Kc of the reverse reaction? What is the relationship?

Brandon Mo 4K

Question:
Which is the stronger base, the hypobromite ion, BrO-, or morphine, C17H19O3N? Justify your answer.

The answer was BrO-.
What is the explanation that BrO- is the stronger base?

Brandon Mo 4K

He did not mention it in class, but I think it is mentioned on the significant figures pdf on his class website.

Brandon Mo 4K

Will we have to memorize any acid and bases? I heard that have to know the strong acid and bases.

If so which are the ones we need to know?

Brandon Mo 4K

Dipole moment is dependent on the electronegativity difference between two atoms. The greater the difference the greater the dipole.

Brandon Mo 4K

What was the reason that transition metals are good for electron transfer?

Brandon Mo 4K

When it comes to polarizing power, I think charge is more important.

Brandon Mo 4K

If the dipole moments cancel each other then the molecule will be nonpolar.

Brandon Mo 4K

Why is AX2E2 bent and not linear?

Brandon Mo 4K

Why does the number of hybrid orbitals equal the number of regions of electron density?

Brandon Mo 4K

But for b), couldn't there be lone pairs that repel each other. For example, one lone pair at the top of the central atom and one at the bottom. However, they would not have an effect on the bond angle since the repulsion forces from the lone pairs cancel each other out.

Brandon Mo 4K

I assume that you are referring to Q8A. If you have two double bonds, it would cause the formal charge on the N to be -1. When you have a negative formal charge, you want to put it on the element with the highest electronegativity, which in this case would be O. You make only one double bond so that...

Brandon Mo 4K

I think we would need to memorize the bond angles of molecules without lone pairs on the central atom. Professor Lavelle said that we do not need to memorize the bond angles for the molecular shapes with lone pairs on the central atoms. But just that the lone pairs have an effect on the bond angles....

Brandon Mo 4K

You want to choose the most stable Lewis structure. This would relate to the formal charges and how you want as many 0's as possible.

Brandon Mo 4K

How does the strength of dispersion forces explain whether a molecule is liquid or solid?

Also, during the lecture on 11/7/18, why does CH4 boil at a lower temperature than CCl4?

Brandon Mo 4K

You can think of distortion as the tendency of the electron density of ionic bonds to occupy the region between two nuclei. As the distortion of the electron cloud on an anion increases, ionic bonds get more covalent character. Atoms and ions with electron clouds that undergo large distortion are hi...

Brandon Mo 4K

Why are double bonds shorter than single bonds?

Brandon Mo 4K

Yukta Italia 3I wrote:When we have to draw Lewis Structures on the midterm do you think we'll have to draw every resonance structure possible?

I think you only need to draw the resonance structures for the most stable structure.

Brandon Mo 4K

I think the 13th column is an exception to the octet rule because the elements in the 13th column have 3 valence electrons. This means that they only need 3 bonds to create a formal charge of 0.

FC = V - (L + S/2)
FC = 3 - 3 = 0

Brandon Mo 4K

Why does the energy order in the same shell: s < p < d < f? Does this have to do with how the s-orbital does not have any nodal planes so there is more electron shielding compared to the other orbitals? Is it the less nodal planes you have, the more electron shielding there is, resulting in lower en...

Brandon Mo 4K

Will every exam have all the things given from the constant and equations document on the class website?

Brandon Mo 4K

During lecture, the equation was given as H(psi) = E(psi).

Do we need to know how to use the equation?
If not, then could someone also explain what the Schrodinger equation is and what we are supposed to know?

Brandon Mo 4K

I think we would have to multiply the radius by 2 to get the diameter. We want delta x to be the full range of where the electron could be.

Brandon Mo 4K

Does basically anything have rest mass? During the lecture, Dr. Lavelle said that photons have no rest mass. Does that mean we can use DeBroglie's equation on anything except photons?

Brandon Mo 4K

What do the deltas in the Heisenberg Indeterminacy equation mean?

Before I thought it meant "change in", but after going to a UA session, delta meant uncertainty.

If delta means uncertainty, what does uncertainty mean?

Brandon Mo 4K

On the class website, it says, "Test 2 covers all quantum material up to and including quantum numbers."

Does this mean that there will not be anything about orbitals or anything in chapter 2 (6th edition)?

Brandon Mo 4K

I am still confused about what nodal planes are. During the lecture, nodal planes were defined to have zero probability of electron density. Does this mean that nodal planes are a region where there would be no electrons found?

Brandon Mo 4K

I think the extent of the change in the electrical field is related to the slope of the wave. As the frequency decreases, the slope of the wave also decreases.

Brandon Mo 4K

What exactly is Rydberg's equation?

In the book, the equation is given as:
v = R((1/n1^2) - (1/n2^2))

Is this the same equation as En = - hR/n^2 or is it something different? Also, how are we supposed to use this formula when working on problems?

Brandon Mo 4K

How do you determine the number for the lower energy level for the hydrogen spectral series (Balmer, Lyman) or is this something that could be found from a chart?

Brandon Mo 4K

During one of the peer learning sessions, the UA talked about how you were supposed to round to an even number when there is 5. I do not remember clearly what the UA said. But if you were rounding 4.45 to two significant figures, it would be 4.4, not 4.5. Will we need to do this for future exams (ro...

Brandon Mo 4K

I believe your answer would be fine because we always want to simplify the coefficients if we can. Generally, I think that it is always better to simplify the coefficients.

Brandon Mo 4K

In order to solve this problem, you have to find out much of the reagents will be able to complete the reaction. It is given that 1 mol B reacts with 1 mol A, but there is only 1 mol A present. Using the given balanced equation: 2A + 1B ---> 3C. You can come up that 3 mol C will be made from every c...

Brandon Mo 4K

I began this problem by multiplying 1.00 mol of Ag by Avogadro's number to get 6.022x10^23 atoms of Ag. Then I multiplied that by 2(144 pm)--144 pm is the radius of the atom, so to get the total length of the atom you have to double it. The end result was 1.73x10^26 pm, which is equal to 1.73x10^11...

Brandon Mo 4K

The field of nanotechnology offers some intriguing possibilities, such as the creation of fibers one atom wide. Suppose you were able to string together 1.00 mol Ag atoms, each of radius 144 pm, into one of these fibers by encapsulating them in carbon nanotubes (see Chapter 7). How long would the fi...

Brandon Mo 4K

Thank you so much. I was so confused because I thought they would be before chapter 1.

Brandon Mo 4K

I have the 6th edition of the textbook and I can not find the answers to the fundamentals section in the back of the book. I do not have the solutions manual yet. Does anyone know where they are located in the 6th edition book or are they just not in there?

Brandon Mo 4K

Is the solutions manual required? I have the 6th edition of the textbook, but I do not plan on acquiring the solutions manual. It was noted on the class website link (Questions About The Textbook?): 'All the readings and homework are from the textbook. The solutions manual has the detailed homework ...

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