CHEMISTRY COMMUNITY

Ashley Lopez 3J

The order should not matter, as long as the cathode is on the right and the anode is on the left. I remember Sapling being specific about having the chlorines on the second line, but again, as long as they are on the correct side it'll be okay.

Ashley Lopez 3J

When is delta G spontaneous? Is the answer different for delta G naught to be spontaneous?

Ashley Lopez 3J

I was also wondering the same thing! They are not part of the reaction or product, but are rather created and then consumed during the process.

Ashley Lopez 3J

This could only happen if all the reactants are in zero-order. This means that the rate law would just equal to k and not be dependent on the concentrations.

Ashley Lopez 3J

Can someone please explain why adding a catalyst increases the reverse reaction? I thought that it would decrease when looking at the graph, but I'm just reading it wrong.

Ashley Lopez 3J

I had the same question and also thought they could be used at any time, however, Log is used for standard conditions and In is used for any conditions. You would choose which one to use based on the information given in the question.

Ashley Lopez 3J

How does the Unique Rate formula work? Are the values both positive and negative or only or the other?

Ashley Lopez 3J

Reactants are only ever part of the slow step if they are in the overall rate law, which is a determinant of a slow step.

Ashley Lopez 3J

What's the relationship between potential energy and reaction progress?

Ashley Lopez 3J

I really liked the Chemical equilibrium topic! Honestly, everything up to midterm 1 was cool.

Ashley Lopez 3J

I read that LogQ and lnQ could be used interchangeably, does this really not change anything?

Ashley Lopez 3J

For Sapling, we had to be specific about the order in which we wrote the balancing reaction, how do we know which compounds to write in what order?

Ashley Lopez 3J

What is the correlation between an oxidizing agent and the positive value of V? I had some trouble understanding this problem.

Ashley Lopez 3J

Why does the mass go down on the X electrode and why does it go up for the Y electrode? Can someone please explain?

Ashley Lopez 3J

For number 7, why did the right hand short notation not carry the coefficients with them? I thought that it had to be written exactly how it was written on the cathode half-reaction.

Ashley Lopez 3J

Why is is that the potential difference between electrodes is positive? What does this mean?

Ashley Lopez 3J

Does a Galvanic Cell always carry water and is it the only liquid that can be used in the cell?

Ashley Lopez 3J

What is the difference between the favorable and unfavorable reactions in Electrochemistry? What sets them apart?

Ashley Lopez 3J

Just how we can remember Oxidation with "LEO", is there an acronym or some way to remember what Reduction is?

Ashley Lopez 3J

The question was:

The internal energy of a system increased by 982 J when it was supplied with 492 J of energy as heat. (a) Was work done by or on the system? (b) How much work was done?

What is part (a) asking me? Can someone please explain?

Ashley Lopez 3J

How can an Isolated system be affected if it is isolated and nothing affects it? What kind of changes have to occur that affect it? I'm having a hard time understanding this still.

Ashley Lopez 3J

From the Second Law of thermodynamics, we know that energy can either increase or remain constant spontaneously, meaning it just occurs and is favored. However, a decrease of entropy is not spontaneous because it is not favored.

Ashley Lopez 3J

When solving for this answer, for the temp equation where it is Tfinal over Tinitial, I switched the numbers and did Tinitial over Tfinal, was this something I got lucky with when I got the right answer or does it not affect the answer when I switch the numbers?

Ashley Lopez 3J

Intensive properties are independent of the amount of substance that is present whereas extensive properties do depend on the amount of substance that is present. These properties are important to know because it helps with explaining changes that occur.

Ashley Lopez 3J

First, you are going to want to find the value of n by using PV=nRT, once you have that value, you substitute it back into the formula. and use the values given to you from the initial question. And remember, the answer has to be positive because the temperature is increasing.

Ashley Lopez 3J

The homework question asks "At constant pressure, which of these systems do work on the surroundings?". How do I go about solving this hw problem when the equations involve letters and no actual numbers?

Ashley Lopez 3J

For part two, when solving for Path B, why is it that in the first step delta V equals zero?

Ashley Lopez 3J

Between the 3 methods Lavelle taught, what is the order of accuracy? Is there one better than the other?

Ashley Lopez 3J

Why is it that sometimes we cross out 4.184 and don't multiply it with the mass? How do we know it is okay to take this step?

Ashley Lopez 3J

Whenever there's a problem regarding Hess's Law, I have trouble knowing which equations I am suppose to flip in order to get the final equation. Are there any right ways to do it or is it more of a trial and error?

Ashley Lopez 3J

When H20 is part of the reactants for an equation, do we assume that it is in its liquid form unless otherwise stated?
So if we were to create our expression for K, we usually just disregard H20.

Ashley Lopez 3J

Can someone please clarify what is meant by "..chemical equation for the proton transfer equilibrium in water..." ?

Ashley Lopez 3J

This problems asks whether CL2 or F2 is more thermodynamically stable. How do we know when something is more thermodynamically stable? The answer was CL2, but I'm not sure why. Can someone please explain?

Ashley Lopez 3J

As far as my understanding goes, this is true because if you have more reactants, in order to minimize that effect, the reaction will go toward the right, so to the products. Also, it mentions equilibrium concentrations and not equilibrium constant. If it were to say equilibrium constant, then the s...

Ashley Lopez 3J

For the reaction N2(g) + 3 H2(g) ⇌ 2 NH3(g) at 400. K, K = 41. Find the value of K for each of the following reactions at the same temperature: (a) 2 NH3(g)⇌ N2(g)+3 H2(g) (b) 1/2 N2(g) + 3/2 H2(g) ⇌ NH3 (g) (c) 2 N2 (g) + 6 H2 (g) ⇌ 4 NH3 (g) Can someone please explain how I would go about solving ...

Ashley Lopez 3J

Why is it important to know if it's a weak or strong base/acid? For the Sapling hw, it would be specific in the question, but the work for all of the hw was very similar. What are some important things to note that make this difference important?

Ashley Lopez 3J

Is there a time when the value of Ka or Kb may equal to 10^-4 or smaller, but it isn't less than 5% of initial? or can we trust the exponent values?

Ashley Lopez 3J

I'm confused on what the percent ionization tells us. Can someone please explain that to me since it was on the Sapling Hw?

Ashley Lopez 3J

The % Ionization is more reliable, so I would suggest that if you're in a position where you're really unsure, then do the % ionization.

Ashley Lopez 3J

At value does H30+ have to be for the solution to be neutral? and why is this important?

Ashley Lopez 3J

Is it possible to create and do the ICE box with mols and not mol.L-1? If so, how would that work with the equilibrium values?

Ashley Lopez 3J

How do we know when we are suppose to put the actual values of initial concentrations and not as 0 as seen in Sapling hw #10? I was confused as to why we put the initial values for both reactant and product.

Ashley Lopez 3J

Temperature is the only condition that could change the value of K. Every other condition changes we've learned so far does not affect the value of K because the system reacts in a way to minimize the effect of said changes.

Ashley Lopez 3J

What are other units, that mean the same, that could be used in equilibrium concentrations besides mol.L-1 and bar?

Ashley Lopez 3J

How do we know when the Change in equilibrium is negative or positive for products/reactants?

Ashley Lopez 3J

Does a change in concentration have or not have an effect on the system? Will there ever be a time when a change in conc changes K?

Ashley Lopez 3J

How do the values of delta H influence the way we determine how there's a shift in equilibrium when there's an increase in temp and vice versa? In other words, what do negative and positive values of delta H mean for the reaction?

Ashley Lopez 3J

How do I know which x value to choose when I have solved for both values of x when I use the quadratic equation?

Ashley Lopez 3J

When we are writing down the Initial concentration, is there ever a time that products will not equal 0?

Ashley Lopez 3J

Are all the cases of cubic equations going to have small values of x where we have to approximate? If not, what is a measurement of knowing when the x is too small and we need to approximate?

Ashley Lopez 3J

What exactly is 2p^2? I saw it on my lecture notes and I am unsure about what that means? Is that a different energy level than 2p or what exactly is it taking into account?

Ashley Lopez 3J

I am a bit confused on the rules of hybridization. Do we have to fill up all of 2s before we move onto p?

Ashley Lopez 3J

For most of the Sapling homework, we had to identify whether the numbers or compounds given were acids or bases.R Regarding the numbers, is there a rule that we can abide to when we determine whether it is acidic or basic? Or is the easiest way is by using the formulas of H+ and OH-?

Ashley Lopez 3J

What is a polyprotic acid and base? and What do they do?

Ashley Lopez 3J

What is meant when they ask to draw box diagrams to show electron promotion and hybridization? What exactly is electron promotion?

Ashley Lopez 3J

How do we find the oxidation numbers? I am still a bit confused on how we find them and my PLF session talked about it, but very quickly and I still don't fully get it.

Ashley Lopez 3J

An Amphoteric compound acid/base is going to be weak, seeing that it can react as either a base or an acid. This also just means that the behavior of the compound depends a lot more on the stronger base/acid it is reacting with.

Ashley Lopez 3J

Dentate is talking about the binding sites of ligands. Something I would use to remember this is seeing that dentate and donate is almost spelled the same/sound similar. (After all, ligands donate e-)

Ashley Lopez 3J

In the Sapling textbook, the definition of a ligand states that it acts as a lewis base by donating e-. This means that in a structure, all atoms that are not the central atom are considered Ligands? I'm a little confused on what a ligand is now, so can someone please clarify.

Ashley Lopez 3J

What prefixes are we expected to know for the naming of compounds?

Ashley Lopez 3J

Is there any repulsion strength between bonding-bonding PR? If it's a bond, how can it have repulsion strength? Or does it just reduce the repulsion strength, but not actually have repulsion?

Ashley Lopez 3J

What is the difference between polar/nonpolar bonds and polar/nonpolar molecules?

Ashley Lopez 3J

One of the answers to the question of which one was polar was CH2CL2. When it is drawn, it looks like it would be non-polar and that there would no zero electric dipole. Can someone please explain why is it polar and why the dipoles do not cancel?

Ashley Lopez 3J

The question asked to draw three possible Lewis structures for C3H4, but none of them were resonance structures, but why is this? It seems like one of them could have been, so why was that not an acceptable answer?

Ashley Lopez 3J

In the homework, a hint for a problem stated "Delocalized π bonds occur when π orbitals extend over more than two atoms", but I'm still a bit confused when it talks about it being a pi orbital? Does it just mean there are more than a single bond between two atoms?

Ashley Lopez 3J

We want to be able to get to a Lewis structure with the least formal charge, always. This is because they'd had the least amount of energy, thus making them more stable and we want that! Also, it is important to remember that we want to always draw these lewis structures on tests

Ashley Lopez 3J

Covalent bonds include both sigma and pi bonds. And yes, sigma bonds are in single bonds, sigma and pi are in double bonds, and so forth.

Ashley Lopez 3J

What exactly is meant by polarizability? I know that it has to do with London forces, but I am a bit confused on what role is has on this type of force.

Ashley Lopez 3J

H20 is bent because the two lone electron pairs that are on one side of the molecule cause a repulsion on the hydrogen atoms attached to the oxygen molecule. The repulsion is ultimately what induces the tetrahedral shape. I visualize it as each lone pair having the energy to push down (or up) on the...

Ashley Lopez 3J

Why are two nearby rod-shaped molecules stronger than when there are two nearby spherical molecules?

Ashley Lopez 3J

Even though they are similar in strength, one of the UAs said dipole-dipole is stronger than dipole-induced dipole. I don't think we need to know that specificity for the midterm, but I just wanted to add on to previous comments.

Ashley Lopez 3J

I'm still confused about what it means when an ionic bond has some covalent bond character. The professor talked about it, but can someone please explain what this means and how it works.

Ashley Lopez 3J

During one of the professor's lecture, he states that P, S, and Cl can accommodate more than 8 valence e-. Then he says it is because atoms in period 3 or higher have d-orbitals that allow them to accommodate. Does this relate to the drawing of Lewis Structures, like when there are some atoms that c...

Ashley Lopez 3J

Adding on, during a PLF session, I learned about Skeletal/Line structures, is there a possibility this may be on the midterm or are we just expected to draw the Lewis Structure with the lest F.C.?

Ashley Lopez 3J

When doing formal charges, do we know it is at the best Lewis structure when the atom with the least electronegativity (the atom in the middle) equals 0? Is that an indication that we could stop or do we just kind of stop when the formal charges of everything is at its lowest?

Ashley Lopez 3J

Hydrogen bonding occurs between an attraction of a hydrogen atom to an electronegative atom like N, O, or F. H atoms will be "automatically" attracted to these atoms in other molecules.

Ashley Lopez 3J

The second ionization energy is greater than the first because once an electron is removed, the other electrons are held tighter since there is one less electron contributing to the negative repulsion.

Ashley Lopez 3J

Because carbon is the central atom, it accepts electrons. Even though both O are negative, CO2 is still partially positive and the double bonds are able to break. The best way to visualize this up is to draw reactions with CO2.

Ashley Lopez 3J

As I'm reviewing past topics, I still find myself confused about 4s coming before 3d, but then there are cases where 3d comes before 4s. I'm not sure if I wrote my notes incorrectly, but for Ca it was [Ar]4s^2, but for Sc it was [Ar]3d^14s^2. Is there a reason why this rules seems to change for diff...

Ashley Lopez 3J

Going off of trends on the periodic table, what are different ways that they could be described instead of just saying from left to right or up and down. I remember one of the questions on the practice Respondus quiz for this week asked about a trend, but the wording of the answers were very confusi...

Ashley Lopez 3J

Can someone please explain why is it that 4s comes before 3d?

Ashley Lopez 3J

A question on Sapling asked us to find the minimum uncertainty. My question is is there a maximum uncertainty or is there only ever a minimum uncertainty? I feel confused just because of the word "minimum". Is there a reason why it's called minimum?

Ashley Lopez 3J

When we are given what n, l, and ml, how would we know how many electrons there are?

Ashley Lopez 3J

There was a question on Sapling that asked, "Identify the reasons why oxygen has a lower ionization energy than both Nitrogen and Fluorine." Can someone please clarify why the answers were what they were?

Ashley Lopez 3J

To follow up on her question,I still get confused when it asks about n2 and n1. Going by the logic of the comments above, this means that n2 is the final state and n1 is the initial state, correct? Or would it be the other way around?

Ashley Lopez 3J

The waves represent the movement of electrons surrounding a nucleus. Electrons can move in waves. These wave patterns must align with each other (usually represented by the variable "n") and if their energies mismatch, then there is no allowed energy level. I am also confused on this topic...

Ashley Lopez 3J

Adding on to her question, how much about orbitals should we know? Are we responsible for knowing the details of s, p, d, and f orbitals and that being it?

Ashley Lopez 3J

Should we know how De Broglie derived lambda=h/p or would we be fine with knowing that h is Plank's constant, p is mass x velocity and lambda is wavelength?

Ashley Lopez 3J

What are some conceptual aspects regarding Wave Properties that might come up on the midterm?

Ashley Lopez 3J

I was working on an example problem and I had to use the formula, E(hv)=(work function) + Ek, but I was confused as to why we had to use this formula and how I know what number is the Work Function. Can someone please explain what Work Function means when it comes to the Photoelectric Effect.

Ashley Lopez 3J

I asked my PLF a similar question and she explained that if needed to 1) it'll explicitly tell us and 2) in the past, he's given a sheet with formulas and we can refer to it. I'm not sure how that's going to work with the test being online though.

Ashley Lopez 3J

Protons and neurons have similar masses, whereas electrons are much smaller and therefore weigh less. Protons and neurons reside in the center of the atom and electrons are floating/orbiting around it.

Ashley Lopez 3J

Any element from Period 3 and below are able to expand, meaning elements like C, N, O are not part of that rule because they are exceptions to it. Reminder to always be careful when you are working with these elements and their surrounding electrons.

Ashley Lopez 3J

Avagrado's number is used when working with moles, so what the professor taught Week 1. For E=hv, the constant that is used is Plank's constant.

Ashley Lopez 3J

There are problems that require you to covert units and the professor has gone over all the units, but my question is whether we have to memorize all of them or which ones should we memorize and which ones don't we have to worry about as much?

Ashley Lopez 3J

The limiting reactant is what determines how much product would be formed, so that is the first step in trying to find the theoretical yield. The percent yield uses both the theoretical and actual yield, so if not ask to be found, then the actual yield will be provided.

Ashley Lopez 3J

There are two formulas integrated into this section of the review. One of them being M=n/v and M(initial)V(initial)=M(final)V(final). I get a bit confused when I try to figure out what formula is appropriate to use for what problem. Are there any key words or any way for me to quickly recognize what...

Ashley Lopez 3J

When balancing chemical equations, I suggest starting off with the element that appear or occurs less times and then move your way to the next elements based off of that. It is important to remember that the coefficients have to be the lowest whole number, so double check. Also, it is okay to multip...

Ashley Lopez 3J

Whenever I'm solving a question, how do I know I can start looking at Sig figs. In other words, can I do it during my scratch work when I'm trying to figure out the final answer or do I use all numbers and decimals until I get to the final answer and then I use Sig Figs?

Ashley Lopez 3J

Hi Caro.
The empirical formula and the molecular formula can indeed be the same. Sometimes the ratio of atoms cannot be simplified further, so there will not be a multiple of said formula.

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