CHEMISTRY COMMUNITY

Nora 1F

I believe that they're related through the equilibrium constant, so that K = k/k'. Stated differently, k = (K)(k')

Nora 1F

How do mean relative speeds and activation energy relate to the collision theory? How is collision theory used to determine a rate constant?

Nora 1F

Can someone please explain what the steric requirement is and why the steric factor must always be less than one?

Nora 1F

If a reactant is zero order, you do not include it in the rate law because it won't affect the rate of the reaction.

Nora 1F

Justin is correct! So just to clarify, a reactant is first order if when all other reactant concentrations are held constant and the concentration reactant of interest is doubled, the rate doubles.

Nora 1F

While reviewing my tests I was unsure about why one of the problems was marked incorrect. The question asked to calculate the standard potential for the following reaction using given reduction potentials. Fe^3+ (aq) + 3e- --> Fe (s) Fe^3+ (aq) + e- --> Fe^2+ (aq) E = 0.77 V Fe^2+ (aq) + 2e- --> Fe ...

Nora 1F

I agree about unique rates, but to further clarify, for unique average rates you do not take the coefficient into account so that the unique rate can be different from the average rate. I found the first page of this study guide to be helpful as well. https://books.google.com/books?id=wwlAfF32x18C&a...

Nora 1F

From what I understand, you are correct about the pre-equilibrium approach. The pre-equilibrium approach should be used when the first step is fast and the following step is slow, while the steady state approximation should be used if the first step is much slower than the following step.

Nora 1F

I believe this was referring to when the concentration of product is low, because when the product concentration is low it is less likely that the backward reaction will be occurring at a significant rate.

Nora 1F

In a redox reaction, the oxidizing agent is what causes something else to become oxidized (by becoming reduced itself) and the reducing agent is what causes something else to become reduced (by becoming oxidized itself). If it would help to see it in different words or for some examples, https://che...

Nora 1F

It also might be helpful to keep in mind that with a concentration cell, the lower concentration should be the product concentration.

Nora 1F

I believe salt bridges contain an electrolyte!

Nora 1F

Can someone explain why there is always an increase in entropy when a process is spontaneous?

Nora 1F

Could someone explain what we use Nernst Equation for and how it relates to cell potential and concentration?

Nora 1F

I believe because we are dealing with a change in temperature and because a change of 1 degree Celsius is equivalent to a change of 1 Kelvin, the answer for this question would have the same numerical value to give +0.8 J/*C

Nora 1F

I believe that 1 bar would be the unit used in the definition of these conditions, but because the difference between 1 bar and 1 atm is so small and we are accustomed to using atm, you will often see them interchanged.

Nora 1F

Why is the max work done by a process at constant temperature and pressure equal to deltaG?

Nora 1F

I don't think you will need to memorize any equations, but if there is one in particular you are unsure about I would expect the equation sheet to be the same as the one given with the first test and on Dr. Lavelle's site.

Nora 1F

The universe would be described as an isolated system because neither matter nor energy are created or destroyed (gained or lost).

Nora 1F

You should decide which one to use based on the units of the constant.

Nora 1F

Yes, I think that in this case because it says assume ideal behavior and you are not given an amount of moles, you assume you have one mole of N2 gas.

Nora 1F

Forgot to add the link above!

http://chemed.chem.purdue.edu/genchem/t ... l.php#hvse

Nora 1F

When heat is released or absorbed during a reaction that takes place at constant volume, you use deltaU. When heat is released or absorbed during a reaction that takes place under constant pressure, you use deltaH. I found the following website to be very helpful in explaining the difference if you ...

Nora 1F

From what I understand, all the enthalpies needed for a problem will be given on the test.

Nora 1F

I believe when you have constant pressure conditions (isobaric), you use deltaH = q+w , and when you have constant volume conditions, deltaU = q can be used.

Nora 1F

I believe that unless otherwise stated in the problem, you should assume standard conditions apply.

Nora 1F

Can someone help clarify when each of the three methods discussed in class should be used. I understand that enthalpy being a state function is the basis of the methods but am not sure when to use them.

Nora 1F

If you're looking for an example of this, problem 8.53 is a good start.

Nora 1F

Rain already answered the question well, but sometimes it just helps to see the process. I found this video helpful and hope it helps you too!

https://www.khanacademy.org/science/che ... -equations

Nora 1F

A Lewis acid accept electrons and Lewis bases donate electrons. Bronsted acids donate protons while Bronsted bases accept protons. A Lewis base does not necessarily have to be a Bronsted acid. When only electrons are being transferred (no protons), you are dealing with Lewis definitions.

Nora 1F

I checked Dr. Lavelle's website and it says that Test 4 will include material from chapter 11 from 11.1 to the end of 11.8, and LCP is mentioned before the end of 11.8 so I would understand what it states to be safe. Also on the chemical equilibrium outline, this is the last bullet: "Use Le Cha...

Nora 1F

For part A, it is helpful to remember that the reverse reaction has a K value that is the inverse of the forward reaction. This is because you find K by dividing the concentrations of the products by the concentrations of the reactants, and if the reverse reaction is occurring, then the numerator an...

Nora 1F

When naming a coordination compound, the ligand names are written first in alphabetical order (before the TM ion). They are written using prefixes to indicate the number of ligands, so the prefix tri- would be chosen over bi- if the complex has three ligands.

Nora 1F

What do you look at to determine the number of ligands in a given complex?

Nora 1F

I just asked the same question and from what I understand now, this is how AXE notation works: The A is the central atom. The X is an atom that is directly attached to the central atom. The subscript n is the number of atoms (bonded pairs) attached to the central atom. The E is the a lone pair of el...

Nora 1F

Can somebody explain how AXE notation is used? Will knowing AXE notations be sufficient for naming molecular shapes?

Nora 1F

For the purpose of this class, I don't believe you will need to draw 3D Lewis structures, but you will need to be able to draw 2D Lewis structures and name the 3D shapes. Hope this helps you narrow down what you have to study!

Nora 1F

Just to clarify, Lewis structures deal with a two-dimensional representation of molecules, so they themselves are not the actual 3D shape. Rather, the VSEPR model is used for this and Lewis structures are useful for counting regions of high electron density when working with the VSEPR model.

Nora 1F

During lecture we learned that some Lewis structures are better representations than others, and that formal charge can be used to figure out which structure is best. My question is when we should calculate formal charges. Do we always have to calculate formal charges and compare structures?

Nora 1F

Just one more clarification, isomers are atoms/ions of different elements that have the same number of electrons because they have lost or gained electrons. Also keep in mind that a group of isomers, say one where the number of electrons is 10, would also include the atom that normally possesses tha...

Nora 1F

When writing the electron configuration of an atom that ends similarly to the following 3p^6 4s^2 3d^9, I remember that after rearranging it to 3p^6 3d^9 4s^2 there is sometimes another step that results in the electron configuration being rewritten as 3p^6 3d^10 4s^1, but I am unsure as to why this...

Nora 1F

In multi-electron atoms, electron-electron repulsion must be factored in when writing electron configurations. In a 2p subshell, for example, there are multiple orbitals, the 2px, 2py, and 2pz orbitals. Each of these orbitals cannot contain more than 2 electrons. However, the way these orbitals are ...

Nora 1F

So to clarify, you are correct in thinking that the work function is equivalent to the energy needed to remove an electron from one atom of an element. This is also referred to as threshold energy. To go back to the equation, the total energy of the photon will be equal to the work function plus the...

Nora 1F

Building on that question, the Rydberg equation is applicable to atoms of different elements, but the other equation -hR/n^2 is only applicable to hydrogen atoms, correct?

Nora 1F

The limiting reactant will always be the reactant that runs out first, thereby making it so that the reaction cannot take place any longer. Sometimes it will be the reactant with the least amount of moles, but many times it will not be. In order to determine which reactant is the limiting reactant, ...

Nora 1F

I was not sure what the term "formula units" referred to in the following problem. Epsom salts consist of magnesium sulfate heptahydrate. Write its formula. (a) How many atoms of oxygen are in 5.15 g of Epsom salts? (b) How many formula units of the compound are present in 5.15 g? (c) How ...

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