CHEMISTRY COMMUNITY

Venus_Hagan 2L

it is e to the power of the other side

Venus_Hagan 2L

Venus_Hagan 2L wrote:Yes, platinum should be used when you do not have a solid in the half-reaction. It is a non-conductive metal, so it is usually the best choice

non-reactive*

Venus_Hagan 2L

if the reactants and products of the half-reaction are not in solid form, you need some type of solid metal as the electrode. Usually, you use Pt(s) because it is a fairly non-reactive metal.

Venus_Hagan 2L

If the temperature is constant, there is no heat change and thus the change in internal energy is zero

Venus_Hagan 2L

Dr. Lavelle,
Thank you for all that you have done for us these past two semesters. I am glad to have had for 14A and 14B. All of the resources and extra effort you put in really made a difference. I appreciate all that you have done for us as a class. Hope you have a great spring quarter :).

Venus_Hagan 2L

You can tell if the reaction is favored based on its delta G. Exothermic and endothermic correlate to the delta H value

Venus_Hagan 2L

i would just finish them tonight just in case.

Venus_Hagan 2L

if there is a question with a catalyst, I think it would be to identify what species is the catalyst in a reaction mechanism

Venus_Hagan 2L

In a basic solution, there will be no H+ ions. You can only add either water or OH-.

Venus_Hagan 2L

the concentration of the reactants have no effect on the rate of reactants

Venus_Hagan 2L

Yes, platinum should be used when you do not have a solid in the half-reaction. It is a non-conductive metal, so it is usually the best choice

Venus_Hagan 2L

if you do not have a solid in your half-reactions, you need to add a non-conductive metal such as Pt(s). I think you can add others but Pt is the typical one

Venus_Hagan 2L

I don't think so because he didn't talk about it in lecture

Venus_Hagan 2L

I don't think so because he didn't talk about it in lecture

Venus_Hagan 2L

Jamie Hwang 2F wrote:is it even still happening? Because someone said that the UA step up sessions will probably be cancelled as they are going home

I believe it is canceled. His email said all of the review sessions and office hours have been canceled.

Venus_Hagan 2L

I know the grades have been posted, but im not sure if we are going to get the actual test back

Venus_Hagan 2L

I would like to know this as well(especially the one with Lyndon)

Venus_Hagan 2L

most of the time when you are dealing with weak acids and bases, you will be using an ICE table

Venus_Hagan 2L

I am pretty sure the final will not be online because at the 1:00 lecture Lavelle showed us the link on his website that tells us where to go to take the test.

Venus_Hagan 2L

Yes. The Standard Hydrogen Electrode is used to measure the standard potential of other electrodes

Venus_Hagan 2L

We use metals like platinum in our galvanic cells when both the reactants and products of a half-reaction are not in a solid-state. For the example of a hydrogen cathode, the H+ ions(aq) are getting reduced into H2 gas. Without a platinum electrode, the electrons can not flow from the anode and get ...

Venus_Hagan 2L

I don't think there are any specific review sessions for test 2

Venus_Hagan 2L

Yes, the number of electrons lost in one reaction should equal the number of electrons gained in the other.

Venus_Hagan 2L

for standard free energy, the temperature is 298 K or 25 degrees C

Venus_Hagan 2L

If you are considering delta T then it is okay to leave in Celcius because both units have the same scale, but if you are just considering temperature then you should convert to kelvins by adding 273.15

Venus_Hagan 2L

I don't believe he will curve the midterm itself. :(

Venus_Hagan 2L

If a molecule consists of all the same atoms or the atoms can be in multiple places within the molecule (resonance) then it has no positional entropy and at 0 Kelvins, the molecule would have no entropy. Ex BF3. If the molecule has different molecules like COF2, then the oxygen can be in multiple pl...

Venus_Hagan 2L

Cv is at constant volume and Cp is at constant pressure

Venus_Hagan 2L

percent dissociation is how much of the acid separated into its conjugate base and a proton compared to the original amount of acid or how much of the base separated into its conjugate acid and OH- compared to the original amount of base. You can calculate it by putting either the concentration of ...

Venus_Hagan 2L

percent dissociation is how much of the acid separated into its conjugate base and a proton compared to the original amount of acid or how much of the base separated into its conjugate acid and OH- compared to the original amount of base. You can calculate it by putting either the concentration of t...

Venus_Hagan 2L

for the ideal gas equation use Kelvin but if you ever need the change in temperature it doesn't matter because both are scaled the same way

Venus_Hagan 2L

a closed system is when matter can not exchange with the surroundings but energy can, an isolated system is when energy and matter both can not exchange with the surroundings

Venus_Hagan 2L

Delta H is the heat of the system at constant pressure, but delta U is heat AND work

Venus_Hagan 2L

ΔU=q+w

Venus_Hagan 2L

The value of R changes based on the units. All of them are given on the equation sheet, so just look to see what units the problem has given you and choose the appropriate one

Venus_Hagan 2L

heat capacity is the most general term focusing on how much heat is required to raise a substance by 1 degree C/K. Specific heat capacity takes into account mass and is how much heat is required to raise 1 gram of the substance by 1 degree C/K.

Venus_Hagan 2L

005162520 wrote:So are we on thermodynamics?

yes we are on thermodynamics/thermochemistry

Venus_Hagan 2L

Add products or remove reactants → toward reactants Add reactants or remove products → toward products if you inc pressure, then shifts toward fewer gas particles if you dec pressure, then shift toward more gas particles For exothermic reactions: inc temp → toward reactants dec temp → toward product...

Venus_Hagan 2L

I have not yet, but I think we are still able to pick up our test this week

Venus_Hagan 2L

You take the ion concentration that the acid or base produces( so if HA is the acid, the ion will be A-) and divide it by the initial concentration of acid or base.

Venus_Hagan 2L

Heat and work are not state functions. The path/steps that are taken to get the value matter.

Venus_Hagan 2L

Kw always is 10^-14 at 25 degrees, but Kb and Ka will change based on the reaction.

Venus_Hagan 2L

Megan Kirschner wrote:Is the only requirement for the calculator that it cannot be graphing?

i believe you can use a scientific calculator or one of the simple four-function ones

Venus_Hagan 2L

i think they both work. it just depends on what you are given for that problem. My TA also mentioned that the difference between the two is very small so we can almost consider them the same thing (no need to convert between the two)

Venus_Hagan 2L

most of the time in 14A we got partial credit. Depends on the TA because they are grading

Venus_Hagan 2L

I don't think the TAs have any control over the chemistry community. I think Lavelle has a system of checking but its not like you need them done before your discussion. Its just by the end of the week so sunday night.

Venus_Hagan 2L

the professor usually doesn't post a practice test

Venus_Hagan 2L

yes they are both solved using the same formula ([products]/[reactants]) but Q is using the concentrations when the reaction is not at equilibrium and K is when it is at equilibrium

Venus_Hagan 2L

Kc is the equilibrium constant using concentrations and Kp is the equilibrium constant using partial pressures.

Venus_Hagan 2L

The expression would be flipped because the products always go on the top and the reactants on the bottom. In a reverse reaction, the products become the reactants and their concentration(s) goes on the bottom now. Similarly, the reactants become the products and their concentration(s) will go on th...

Venus_Hagan 2L

i believe aqueous solutions are included only pure liquids like H20 are excluded.

Venus_Hagan 2L

it can be any five questions that fall under the chemical equilibrium section on the syllabus

Venus_Hagan 2L

if the complex (so the central atom and its ligands) has an overall negative charge then you add the ending -ate.

Venus_Hagan 2L

The two different names are because there are two different sets of naming rules. The book uses one and Lavelle used another in class. I think either is fine.

Venus_Hagan 2L

I think so. If you have 2 regions of electron density it will always be sp, 3 regions is sp2, 4 regions is sp3, 5 regions is sp3d, and 6 regions is sp3d2.

Venus_Hagan 2L

I believe it is just iron and copper. They would be ferrate/ferrous and cuprous/cuprate.

Venus_Hagan 2L

Stong acids have a weak conjugate base and strong bases have a weak conjugate acid,

Venus_Hagan 2L

Bronstead acids and bases focus on what is happening with the protons. What is giving up and H+ and what is gaining an H+? Lewis acids and bases focus on the electron. What is giving up an electron and what is gaining an electron ?

Venus_Hagan 2L

i honestly just memorized them. In the textbook, table 9C.1 is a list of the common ligands with their names, formulas, and charges

Venus_Hagan 2L

the equation sheets from the last test didn't have the formula for Ka but pH was on there

Venus_Hagan 2L

It will be cobaltate because the complex overall has a negative charge. The F6 gives it a -6 charge and the K3 is a plus 3 charge. That means for the entire coordination compound to be neutral then cobalt is a +3. Despite the cobalt itself having a positive charge, the complex or what's in brackets ...

Venus_Hagan 2L

The coordination number is basically how many ligands are attached to the central atoms while the oxidation number is the charge of the transition metal.

Venus_Hagan 2L

i think technically both are right. I would stick with cyano because that's what Professor Lavelle used in class

Venus_Hagan 2L

The transition metal and all its ligand will be inside the brackets and then everything else is outside. If you are going from a name to the formula everything in the complex will be one word and then things outside will be another word.

Venus_Hagan 2L

Basically strong acids dissociate completely and become ions while for weak acids some of it will dissociate and some will remain as acid.

Venus_Hagan 2L

the formula for kA = [A-][H+] / [AH]. i dont think we need to solve for it in this class but its good to know what it is and what it means

Venus_Hagan 2L

you have to use the latin versions so it would be ferrous or ferrate

Venus_Hagan 2L

strong acids fully dissociate and become ions in water. weak acids dont dissociate completely and some of acid still remains.

Venus_Hagan 2L

In lecture, Lavelle said that Lewis acid and bases always produce salt but not always water. Bronstead acids and bases always produce water and salt.

Venus_Hagan 2L

the coordination number is pretty much how many ligand are attached to the central atom

Venus_Hagan 2L

if the complex has an overall negative charge you would add -ate to the end of the metal's name

Venus_Hagan 2L

i think we will only see coordination compounds with transition metals

Venus_Hagan 2L

Maya Pakulski 3D wrote:Why are there there two definitions for acids and bases? Why not just one?

the two definitions focus on different things. Bronstead focuses on the transfer of protons or H+ ions and Lewis focuses on electrons

Venus_Hagan 2L

They pretty much happen in all molecules all of the time because the electrons are always moving and can pile up on one side temporarily at any time.

Venus_Hagan 2L

We do not need to know how to draw the 3D models with the bold and dashed lines. We just need to draw Lewis structures and know the shapes.

Venus_Hagan 2L

We don't care about whether it is a single or double or triple bond. We consider them all a single region of electron density.

Venus_Hagan 2L

I don't think so because double and triple bonds are still considered one region of electron density.

Venus_Hagan 2L

I think the notation would just not include E at all. It could look something like AX5

Venus_Hagan 2L

Noble gases typically are not included in the periodic trends. For electronegativity, they would have a very low value due to their filled valence shells.

Venus_Hagan 2L

I think for this we would need to know that orbitals look the way they look because they have certain nodal planes where the electrons have a zero probability of existing. So like the p orbitals have two lobes because there is a nodal plane where an electron will never exist, and the s orbital is sp...

Venus_Hagan 2L

The effective nuclear charge is the net charge of the protons in the nucleus after taking into account the electron shielding. If you take away some of the electrons, the amount of electron shielding will decrease and the higher your effective nuclear charge will be.

Venus_Hagan 2L

The central atoms should be the least electronegative atom. My TA also mentioned that if you have a molecule and its like one of an element and 4 of another then the central atom will probably be the element that only has one.

Venus_Hagan 2L

Did you hear about oxygen's date with potassium ??

It went OK.

Venus_Hagan 2L

You only fill the 3d orbital before finishing the 4s orbital for Chromium and Copper (for this class because we don't go past the first row of the d-block). This happens because Cr almost has a half-filled d orbital and copper almost has a fully filled d orbital. A half or fully filled d orbital is ...

Venus_Hagan 2L

I think Copper and Chromium are the exceptions we have to worry about for this class. They are different because they almost have a half-filled or filled d orbital. Having a half-filled or filled d orbital is more stable than the filled 4 s orbital and so it takes one of the 4s electrons. The electr...

Venus_Hagan 2L

Kennedi3K wrote:Is this the same for ionization energy?

Yes the trend for ionization energy also increases as you go up and to the right.

Venus_Hagan 2L

Based on Hund's Rule, electrons will always start parallel and fill up all of the orbitals with only one electron before going back and pairing up.

Venus_Hagan 2L

I personally like to watch videos on youtube or khan academy for topics that I don't quite understand. One really great YouTuber is Bozeman Science.

Venus_Hagan 2L

I think Professor Lavelle said in class that the resonance structures will be drawn with the double-sided arrows.

Venus_Hagan 2L

I think the modules are one of the most helpful tools for me because I am able to strengthen my understanding of the topics taught in lectures. It is easy to pause or rewind the video when you are confused, and the post-assessment questions are really helpful to make sure you know how to apply the c...

Venus_Hagan 2L

I am pretty sure we just have to know the first row for the d-block.

Venus_Hagan 2L

The 1 and 2 are the names of the energy levels. It not like final and initial. When an excited electron starts at some higher level (2,3,4 or 5) and falls to the 1 energy level then it is in the Lyman series. When the excited electron starts at some higher level (3,4,or 5) and falls to the 2 energy ...

Venus_Hagan 2L

An electron is not ejected because increasing the light's intensity only increases the number of photons. If your 10 photons don't have enough energy, adding 50 more of the same energy won't cause the electrons to eject. You must increase the energy of each of the photons allowing each to overcome t...

Venus_Hagan 2L

I would say to try to balance the most difficult molecules first. Some molecules like O2 that are just one element can be easily adjusted without effecting other things you have previously balanced. If you leave these towards the end, then you will have to do less adjusting overall.

Venus_Hagan 2L

Don't trust atoms, they make up eveything.

Venus_Hagan 2L

The experiment needs to have 60 ml of the 0.5M solution. If you did not add the extra 48 ml of water, it would not be the right volume or molarity.

Venus_Hagan 2L

Hi :) I just wanted to confirm that the homework due for week three should be from the quantum world section.

Venus_Hagan 2L

Similar to everyone else, I have been going under the quick links section and keeping track for myself how many posts I have made.

Venus_Hagan 2L

I believe they are an extra resource to use for comprehension. I do not think that have a set deadline.

Venus_Hagan 2L

If it is a hydrocarbon that is combusting and it combusts completely, then its the hydrocarbon and O2 on the reactant side and CO2 and H2O on the product side.

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