CHEMISTRY COMMUNITY

Brandon Valafar

They are just to help you get to the 50 points, its like extra time.

Brandon Valafar

Usually results are given in week but since this test was multiple choice I'd expect it to be earlier.

Brandon Valafar

Oxidizing agent gains electrons while the reducing agent loses electrons. It's kinda like the opposite as usual.

Brandon Valafar

Ecell o is the standard cell potential in standard conditions using standard reduction cell potentials. Ecell is the cell potential not in standard conditions.

Brandon Valafar

n should be the number of electrons transferred

Brandon Valafar

You add Platinum when the reduction reaction or the oxidation reaction does not have a solid metal element in it to conduct the electrons.

Brandon Valafar

The free energy available to do work.

Brandon Valafar

Since all the cell potentials are given for reduction reactions, we have to flip the equation and the cell potential to get it for cell potential for the oxidation reaction, for the anode.

Brandon Valafar

I don't think so, I think he just wants you to "know" them but they won't appear on an exam.

Brandon Valafar

The way I do it is however many electrons are in your balanced equation after you multiply and match the coefficients.

Brandon Valafar

Kinetics focuses on how the reaction progresses over time. Thermodynamics focuses on the the initial and final rates.

Brandon Valafar

You flip E for oxidation because all the E values are given for reduction reactions. Therefore to flip the reactions to oxidation you have to also flip the E.

Brandon Valafar

If you write out the separate oxidation and reduction reaction then add them together after creating like coefficients for the electrons, you will see that it ends up with the anode being in the products and the cathode being in the reactants.

Brandon Valafar

You add platinum when there is no other solid metal in the oxidation reaction or reduction reaction.

Brandon Valafar

Yes. Reduction occurs at the cathode and it is placed on the right of the cell diagram while oxidation occurs at the anode and that is placed on the left of the cell diagram.

Brandon Valafar

My guess would be that it's going to be more on thermodynamics and kinetics, since we weren't tested that much on thermodynamics on the midterm and kinetics is what we just learned.

Brandon Valafar

The larger K is, the shorter the half life is. They are inversely related.

Brandon Valafar

A represents the concentration of the reactants and A0 represents the initial concentration.

Brandon Valafar

A cell can do work when Ecell is greater than zero, meaning that the cathode must be greater than the anode.

Brandon Valafar

Its the number of species (reactant molecules, ions, or atoms) that are in an elementary reaction.

Brandon Valafar

Probably in the last discussion section this week.

Brandon Valafar

Having 100 posts should be acceptable. I think that they start checking from the date of when the quarter started and on.

Brandon Valafar

Can someone help me understand the half reactions for part D of 6L.3? Specifically the oxidation reaction.

Brandon Valafar

I'm going through problem 6L.3 part b and can't seem to find the standard cell potential for the half reaction for h2? is there a rule im supposed to know?

Brandon Valafar

A state function doesn't rely on the pathway taken, it only relies on the initial and final values.

Brandon Valafar

State functions are independent values regardless of the pathway to get to the final value. The quantity only matters based on the final and initial values, and not the pathway to get there.

Brandon Valafar

If the delta G value is negative, then it is spontaneous toward the forward direction.

Brandon Valafar

Since the electrons flow from the anode to the cathode, the cathode has a positive charge to attract the electrons, and the anode has to stay negative. The salt bridge lets this happen.

Brandon Valafar

Oxidation: loses electrons. Reduction: Gains electrons.

Brandon Valafar

Yes! NH4CL will dissociate into NH4+ and Cl- since NH4CL is inside a solution.

Brandon Valafar

Usually depends on the units in the given in the problem and what equation the problem entails in using. I usually always conver from C to K just to be safe unless it asks for it in units celsius.

Brandon Valafar

Removing NO would make the reaction produce more reactants to balance out the reaction. Therefore NO2 partial pressure would decrease

Brandon Valafar

Test 2 starts the tuesday of week 9 and will cover the last page of the outline for thermodynamics and outline 5 of electrochemistry

Brandon Valafar

Electrons are lost for oxidation and electrons are gained for reduction.

Brandon Valafar

Delta G has to be negative for a reaction to be spontaneous. Therefore, when delta G is negative, it means products are formed. When delta G is positive the reaction is not spontaneous and reactants are formed.

Brandon Valafar

Yes! They do cancel out. We balance out the reactions so there is the same number of electrons lost on one side are gained on the other for them to cancel.

Brandon Valafar

Delta S equals delta H over T which is temperature.

Brandon Valafar

I have been told that he does not curve the midterm, however, he does curve the class grading scale at the end of the quarter by just a little bit.

Brandon Valafar

Test 2 was moved to week 9 and will cover the last part of the outline for thermodynamics and will cover electrochemistry as well.

Brandon Valafar

I believe it son the equation sheet, and if not, it's pretty easy. K=273.15 +C

Brandon Valafar

K=273.15+C, so they are interchangeable.

Brandon Valafar

What is the difference between qv and qp?

Brandon Valafar

Yes it is a state property since it is the Final internal energy minus the initial internal energy.

Brandon Valafar

This means that there is no change in pressure and no change in volume.

Brandon Valafar

Lewis acid accepts electron pair, and lewis base donates electron pair.

Brandon Valafar

closed systems can be impacted by their surroundings while isolated systems cannot.

Brandon Valafar

You only count the gas atoms first. Then, moles go based off of coefficients, not the subscript.

Brandon Valafar

Has Lavelle done these yet? I feel like he skipped straight to 4C and 4D since I'm trying to do the earlier sections and am having trouble looking for notes on them.

Brandon Valafar

Yeah those are correct. If you go on the syllabus it says to do those problems.

Brandon Valafar

It depends on the units. If the temperature is given in Celsius which it usually is you don't have to.

Brandon Valafar

From what I understand, you do the least amount of sig figs in the problem behind the decimal for pH. The link on Lavelle's website has a more in depth description though.

Brandon Valafar

How can I tell whether a reaction is exothermic or endothermic?

Brandon Valafar

Why is cl2 more thermodynamically stable than f2 for part c of 5I.13?

Brandon Valafar

Hey I'm really confused on number 5H.1! Can someone please help or tell me if there are any rules I'm supposed to follow?

Brandon Valafar

What is the difference between the heme complex and porphyrin and what do I need to know about each?

Brandon Valafar

What is the correct naming for the compound Na3[Co(C2O4)3] ?

Brandon Valafar

How do we know when to include a coefficient in front of the hybridized orbitals? And what coefficient do we put in what situations?

Brandon Valafar

How do we know when to include a coefficient in front of the hybridized orbitals? And what coefficient do we put in what situations?

Brandon Valafar

Yes it does matter. Iron is one of the naming exceptions where it has a different name instead of just adding -ate to the end to become ironate.

Brandon Valafar

While I don't think it matters too much, I am not 100% sure. However, much of it is just common sense. Acids have their hydrogen in the front, while many molecules have their oxygen at the end.

Brandon Valafar

Bronsted Acid's and Bases are based on protons while Lewis Acid's and Bases are based on electrons. Bronsted acids are proton donors and bronsted bases are proton acceptors while Lewis acids are electron lone pair acceptors and Lewis bases are electron lone pair donors.

Brandon Valafar

I believe there isn't a difference and have seen Lavelle use the old ones in the lecture slides as well. I'm sure both naming methods will be accepted on the exam.

Brandon Valafar

HCO3- will be reacting with water and will pull and accept a proton from the water atom so the products/other side of the equilibrium will be H2CO3 and OH-.

Brandon Valafar

They mean the same thing and just are different conventions. I'm going to use Lavelle's naming scheme since it is on his website.

Brandon Valafar

I don't think it would hurt to know the basic ones however when I've asked TAs they said that we would not be tested on that and that it would be mostly formulas.

Brandon Valafar

Lewis Acids are electron pair acceptors while Lewis Bases are electron pair donors. For 6A.13 (a), when you draw out the lewis structure for NH3, you realize that the N atom has an extra electron lone pair. This means that it will donate the lone pair through a bond, meaning that it is a Lewis base.

Brandon Valafar

The final is 8 questions (definitely with multiple parts each) and it is cumulative so it includes everything we've learned in this course.

Brandon Valafar

H20 can form 4 intermolecular hydrogen bonds.

Brandon Valafar

For finding NH4Cl in an aqueous solution, why does Cl- not impact the pH and why do we leave it out of the equilibrium equation? Furthermore, when do we know to leave out atoms when dealing with salts in equilibrium equations?

Brandon Valafar

BrO- **** not BrO2

Brandon Valafar

I'm having a hard time how to identify which acids are stronger and which bases are stronger. Please help with this problem!!

Which is the stronger base, the hypobromite ion, BrO2, or
morphine, C17H19O3N? Justify your answer.

Thank you.

Brandon Valafar

Square planar always has two lone pairs and has bond angles of 90 degrees.

Brandon Valafar

The best way to tell is to write out the equation and gauge which is an acid and base in the reactants and bases. Yes, the conjugate acids and bases will always be in the equation.

Brandon Valafar

I believe we need to know some of the names of the common acids and bases but nothing too crazy.

Brandon Valafar

CaO is a Lewis base and because it is a metal oxide it will be a STRONG base that will be completely ionized (disassociated) in water leaving only Ca2+ and hydroxide ions.

Brandon Valafar

There is a sheet on Lavelle's website called "Naming Coordination Compounds" which gives you a list of the common compounds/ligands in Chem 14A and their names. I put these on flashcards and that helped me a lot.

Brandon Valafar

My TA gave ours back after the lecture on Monday, but I think a lot of people are getting them back in discussions.

Brandon Valafar

How do we know which ligand to put in the name first if there are two different ligands in the coordination compound? Thanks.

Brandon Valafar

I've noticed that for some problems in the textbook that they do not add the "mono-" prefix when specifying how many of a ligand are in a compound. They simply just write the name of the ligand instead. Should we still write mono- when naming them regardless?

Brandon Valafar

Hello, when should we use cobalt versus cobalt-ate in naming coordination compounds? Not just for cobalt but for transition metals in general, I seem to get confused on this topic.

Brandon Valafar

For intermolecular hydrogen bonds, can hydrogen only bond to NOF atoms (with lone pairs) that are also attached/bonded to a hydrogen beforehand, or can they attach to any NOF atoms with lone pairs even if they aren't attached/bonded to a hydrogen beforehand within their molecule? TL;DR - Can hydroge...

Brandon Valafar

Hello,

For hydrogen bonding, would a Nitrogen atom having two lone pairs be considered as TWO hydrogen bonding sites or one? In other words, is one atom a hydrogen bonding site or one lone pair?

Brandon Valafar

If there are lone pairs of electrons, those make the angle a little bit less than what it actually would be, due to repulsion.

Brandon Valafar

The geometry includes the lone pair electrons while the shape does not.

Brandon Valafar

I believe we only need to know the ones he goes over in the lectures.

Brandon Valafar

You could try to visualize the model of each shape, however I believe it's just one of those things you have to memorize. It will most likely be tested on so make sure you have it down.

Brandon Valafar

When or what week is test 2 supposed to be? Is it supposed to be during week 8 or 9?

Brandon Valafar

Most likely we'll have to know the types of bonds and some background of lewis structures, but other than that I think it is mostly just VSPER model and forward.

Brandon Valafar

How many bonds would Nitrogen and Oxygen like to have?

Brandon Valafar

Is there any periodic trend for polarizability?

Brandon Valafar

Is there any periodic trend for polarizing power?

Brandon Valafar

Only up to 2D will be tested so any chemical bonds after that will not be on the midterm.

Brandon Valafar

We've been covering chemical bonds recently, so I would say to do those. That will also help prepare you and help you understand the material as well and be on topic in TA discussion sessions.

Brandon Valafar

Non-metals are normally receiving or taking electrons from those atoms they are sharing with.

Brandon Valafar

I am so confused on this problem? Can anyone help?
How many orbitals can have the following quantum numbers in an atom:(a)n=2,l=1; (b)n=4,l=2,ml=-2; (c)n=2;(d)n=3,l=2,ml=1 ?

Solutions manual says the answers are 3,1,4,1 but I have no idea how they got that.

Brandon Valafar

In the textbook it says that h bar in the uncertainty equation is equal to h/2pi. However, in our notes it says that the hbar formula is h/4pi. Which are we supposed to use?

Brandon Valafar

If you're referring to the higher energy situation with 3d and 4s, then the rule is that if you can change from d9s2 to d10s1, or from d4s2 to d5s1, you must do so.

Brandon Valafar

I'm sure normally we will use the p3 form since it is much easier and standard. However if a question is asking you to specify I think that's when you use the xyz format.

Brandon Valafar

Yeah we do 5 problems from quantum. We are still on this unit so it only makes sense to do problems from it.

Brandon Valafar

The angstrom conversion is 10e-10. The easiest way to convert for me is to convert from whatever unit it is to meters, and then from meters to angstroms so you don't get confused with the other conversion factors.

Search found 112 matches