CHEMISTRY COMMUNITY

Connor Ho 1B

H2O is water and H2O2 is hydrogen peroxide. What is H2O4?

Drinking.

Connor Ho 1B

Does anyone know of a real-life example of electrolysis? Where does electrolysis take place in daily life?

Connor Ho 1B

Can someone show me how stoichiometric coefficients affect the integrated rate law and half-life? I know that the general integrated rate laws are assuming the coefficients are 1, but if there are coefficients, would the law change?

Connor Ho 1B

Lavelle said this in his email: The three-hour closed-book exam that was scheduled for Sunday is also cancelled. In its place will be a short, straightforward, open-book, take-home final posted on my class website. Again, I will email you the link when the take home final is posted on my class websi...

Connor Ho 1B

Whichever one has the more positive E naught is the reaction that will have a component that will be reduced.

Connor Ho 1B

It's in the chart, maybe you just missed it. It's H2 --> 2H+ + 2e-

Connor Ho 1B

Does the rate constant have units to tell us the units of the half-life? Or does the half-life have generic units?

Connor Ho 1B

I'm not sure if this is your question, but if the product and reactant are the same, then the anode will be the one with the lower concentration and the cathode will be the higher concentration.

Connor Ho 1B

Pt is only needed when there isn't a solid metal to act as an electrode; so yes, if both are aqueous, then you will need Pt to act as the electrode.

Connor Ho 1B

I think Q should be .005/0.15 from the given you wrote out. Maybe that was the error?

Connor Ho 1B

n is in moles of electrons, which is canceled out by the units of the Faraday constant

Connor Ho 1B

It means that the E is not spontaneous, and the cell will not have an electron flow.

Connor Ho 1B

I don't think platinum is necessary for alkaline metals.

Connor Ho 1B

Yes, always leave out the coefficients. I believe you add platinum when there is no solid metal to act as an electrode to move electrons from anode to cathode.

Connor Ho 1B

The solid metal forms when electrons are added to the solution in which the cathode is in. In your example, the cathode would be in aqueous gold, and would gain electrons, forming solid which is attracted to the cathode.

Connor Ho 1B

Salt bridges serve to move anions from the cathode to the anode in order to keep both solutions neutral while the galvanic cell is working.

Connor Ho 1B

The way the solutions manual does it is so that you are solving for -log[H+], which is equal to pH. I think a simpler (or more understandable) way of getting to pH would be this: Given: 0.06V= -(0.0129 V) ln[H+] 2 Using log rules, you can bring the exponent down into the coefficient: 0.06V= -(0.0129...

Connor Ho 1B

Yes, I believe galvanic cells are always spontaneous, meaning E must be positive. Lavelle compared them to batteries, and batteries are always +E.

Connor Ho 1B

Cl- acts as an anion in the cell, which does not affect the electron transfer; it is only used to make sure the solutions stay neutral while the electron transfer occurs, at least from my understanding. Once Cl- and H2 concentrations are equal in both the anode and cathode, the E = 0.

Connor Ho 1B

There won't be any worksheets like there was for the midterm, however you can try to do the homework questions that are on the outlines for practice on the test, since in general most of the problems on the test reflect the homework!

Connor Ho 1B

I think that since it is possible that Fe can be a stronger reducing metal compared to Co, we assume that it is higher on Volta's list. but the wording on this question is definitely whack. lol

Connor Ho 1B

E = -work/Charge

Where charge = (moles e- transferred)*(Faraday's constant

OR

Work_max = -nFE

Connor Ho 1B

All free elements (like ozone, along with O2, H2, N2, etc.) have oxidation numbers of 0.

Basically, there are no electrons moving from the reaction of O3 <--> O2. That's why we say the oxidation number is 0.

Connor Ho 1B

Lavelle usually announces those at the end of week 9 or beginning of week 10.

Connor Ho 1B

I believe you use H+ only, since H2O is used to balance oxygen.

Connor Ho 1B

Since the concentration of K+ is higher outside, that means it is the anode (since in concentration cells, anodes are the ones with higher concentration).

Connor Ho 1B

Since there is no solid metal in the reaction, KOH is needed to drive the reaction. I think you could compare it to why we add Pt into the equation even though it might not be in the half-reaction (in this case KOH is more reasonable since there is hydroxide in the reaction? I'm not completely sure ...

Connor Ho 1B

Maybe the half-reactions in this post will help clear it up: viewtopic.php?f=139&t=60493

Hope this helps!

Connor Ho 1B

On the test, I believe we will be given a gradient table on it, or at least the E^° values so that we can compare.

Connor Ho 1B

Once Au (s) is oxidized, it becomes aqueous in solution as it loses electrons. Think of it as Au being the electrode, which starts to erode as oxidation occurs.

Connor Ho 1B

I don't believe we include H2O in the cell diagram at all since I haven't seen it done for most cell diagrams. From my understanding, it's because H2O is considered a solvent in most diagrams.

Connor Ho 1B

If it's true that the solutions manual treats Cu as the anode, then we would check by adding the standard cell potentials to see which configuration (flipping the E in order depending on which you determine as oxidizing and reducing) gives us a positive Ecell value (assuming we are talking about gal...

Connor Ho 1B

See this post. Hopefully it helps! viewtopic.php?f=139&t=60493

Connor Ho 1B

The half-reaction for the anode would be O 2 (g) + 4H + (aq) + 4e - --> 2H 2 O (l) For the cathode: O 2 (g) + 2H 2 O (l) + 4e - --> 4OH - (aq) Since the anode is oxidized, we flip the half-reaction: 2H 2 O (l) --> O 2 (g) + 4H + (aq...

Connor Ho 1B

Given the cell diagram, you can usually assume that the left side is the anode and the right side is the cathode. If there is a table, find an equation that includes both of items in the anode/both of the items of the cathode to use as a basis for your half-reactions (the items in this cell diagram ...

Connor Ho 1B

It's most likely a concentration cell, which we went over in class. The lower concentration is the reducing agent (is oxidized) and the higher concentration is the oxidizing agent (is reduced).

Connor Ho 1B

Should be true, but also reference the second page of the thermochem outline and the whole electrochem outline for a full look at what'll be on the test

Connor Ho 1B

total pressure = sum of partial pressures

for example, in a system with h2 and o2, where the partial pressure of h2 is 1.2 atm and o2 is 3.2 atm, the total pressure would be 1.2 + 3.2 = 4.4 atm

Connor Ho 1B

If the reactant is a solid.

Connor Ho 1B

I believe that it's a typo either with the manual or the textbook, I got a negative answer as well

Connor Ho 1B

I think Lavelle said in class that he draws Lewis structures only for us to better understand what is going on, although I don't know if this means that we will ahve to in the future or not.

Connor Ho 1B

In simple terms, Le Chatelier's principle is the idea that equations that go to equilibrium, when altered by external factors, will always go back to equilibrium. For example, if I added more product to an equilibrium equation, then the reaction would produce more reactant in order to balance out. T...

Connor Ho 1B

For part (a), here's how I went through it: 1. Create an ICE box for the equation. Since NH 3 is a weak base, there must be an ICE box to solve for pH and pOH. NH 3 (aq) + H 2 O (l) ⇌ NH 4 (aq) + OH - (aq) I: 0.057 M, 0, 0 C: -x, +x, +x E: 0.057-x, x, x 2. From the t...

Connor Ho 1B

Calculate the molar concentration of OH − in solutions with the following molar concentrations of H 3 O + : c) 3.1 M In the solutions manual, it says you divide 10 -14 by 3.1 x 10 -3 to get 3.2 x 10 -12 . Is this an error with the solutions manual/textbook (because the molarity of H 3 O + does not m...

Connor Ho 1B

State whether reactants or products will be favored by an increase in the total pressure (resulting from compression) on each of the following equilibria. If there is no change, explain why that is so. d) 2 HD (g) + H 2(g) ⇌ D 2(g) Why is the answer no change? Is it because t...

Connor Ho 1B

Kc is used when one or more of the products and reactants are in the aqueous phase.

Kp is used when one or more of the products and reactants are in the gaseous phase.

Connor Ho 1B

In this specific problem, I would assume that the K is Kp since the partial pressures are measured. I think that for the tables, the K would have to be inferred as Kp, although Lavelle said in class that K is often used as another way to infer Kc and Kp.

Connor Ho 1B

In class today, Lavelle went over how to find the concentration if you know the partial pressure, and vice-versa using the ideal gas law (P = concentration * RT). Since it asks for the Kc in this question, you would have to find Kc instead of Kp.

Connor Ho 1B

Hg is not included because it is a liquid; liquids and solids are never included in K expressions.

When the items in the reaction are gases, use partial pressure. When they are aqueous solutions, use concentration.

Connor Ho 1B

Aqueous solutions do contribute to the K expression since those solutions can change in concentration (measurably) over time.

Connor Ho 1B

I think the extent of what you need to know about titrations for the final is that it is used to find the pH of a solution, and this is found at the solution's equilibrium point (H+ = OH-)

Connor Ho 1B

Can someone please explain how myoglobin/hemoglobin are related to the heme complex, and what we should know about it for the exam?

Connor Ho 1B

SarahSteffen_LEC4 wrote:On question number 21 of the Marshmallow review. Why does iron have a +2 charge if two of the nitrogens on the porphyrin ligand have a +1 charge?

The two nitrogens actually have a -1 charge, not +1.

Connor Ho 1B

Carbonate is mono- or bidentate because there could be only one area where it will bond or two, depending on the atoms it is reacting with.

Connor Ho 1B

You should memorize cisplatin, the heme complex, myoglobin, and hemoglobin, as well as the properties of AT and GC pairs in DNA.

Connor Ho 1B

If you're talking about cisplatin, [Pt(NH 3 ) 2 Cl 2 ], the reason why it's effective is because the two Cl's are able to be replaced with the nitrogens on a guanine strand, halting DNA replication. If this was transplatin (where the Cl's would be on opposite sides) it would not be as effective beca...

Connor Ho 1B

Just remember that in any geometry, lone pairs are placed as far as possible from other atoms and try to interact with other atoms as little as possible. Put the lone pair wherever it is next to the least amount of atoms.

Connor Ho 1B

HCl, HClO3, HClO4, HI, HBr, HNO3, HSO4 are strong acids

anything with OH- in it is a strong base.

Connor Ho 1B

I believe its because we should know that strong acids completely dissolve in water, while weak acids don't.

BrO₃^- is the conjugate base of a weak acid, so it is a strong base.

Morphine in relativity is a weak base because of the lone pair on Nitrogen, which has weak basic character.

Connor Ho 1B

MMckinney_4H wrote:For number 34, why are two moles of OH produced for every mole of CaO?

CaO completely disassociates in water so:

CaO = Ca⁺ + O^2-

If this were to further react in water, Ca+ would stay disassociated, however

O^2- + H₂O = 2OH^-

after the equation is balanced.

Connor Ho 1B

Kyla Grunden 1L wrote:How do you determine at what point the nitrogens are too far away to bond to the same metal atom?

I believe Lavelle responded to a question about coordination compounds, and in his answer he says that there can be two spacer compounds in between a bonding area.

Connor Ho 1B

As and Bi are both grouped with the amphoteric oxides that are grouped along the metalloid line. The reason why is because when these are reacted with either an acid or a base, it is treated as the opposite; meaning, if it was reacted with an acid, it would act as a base, and vice-versa.

Connor Ho 1B

Ligands are considered Lewis bases because they contribute e- to the coordination complex.

Connor Ho 1B

Acid rain is largely due to CO2 emissions, so yes, decreasing these emissions would be the only way.

Connor Ho 1B

I don't believe there is a limitation to what shape chelating structures can be. As long as it is a chelating polydentate ligand, then there shouldn't be an issue.

Connor Ho 1B

For the most part, as long as you know the original name of the compound, the ligand is usually named by replacing the suffix with -ato or -o. ex. carbonate becomes carbonato, oxalate becomes oxalato, hydroxide becomes hydroxo. There are only a few special ones, ex. en, edta, and isothiocyanto that ...

Connor Ho 1B

Ligands in alphabetical order first, then the metal cation last with oxidation state following.

Connor Ho 1B

Yes, I believe you treat them like a lone pair.

Connor Ho 1B

Lone pairs are never included in molecular shape

Connor Ho 1B

The sapling lessons helped me a lot with understanding coordination compounds.

Connor Ho 1B

I believe the same topics work but in reverse, i.e. the more electronegative, the weaker the base, since bases are e- donors.

Connor Ho 1B

No, generally all sigma bonds are in hybridized orbitals.

Connor Ho 1B

I believe so, and I believe this means cisplatin in is bidentate.

Connor Ho 1B

Technically, yes. But the amount of forces a molecule has also plays a role, i.e. if a molecule experiences both h-bonding and dipole-dipole vs. h-bonding and LDF.

Connor Ho 1B

Lavelle uses acid rain as an example of how CO2 reaction in the environment with water. CO2 reacts in the atmosphere to make acid rain, and with global warming/greenhouse effect, CO2 emissions are more and more prevalent in biology.

Connor Ho 1B

Madeline Phan 4H wrote:Also, why are there p orbitals that are filled along with the hybridized orbitals?

filled p-orbitals generally represent the ability for pi bonds to form.

Connor Ho 1B

Can someone define what heme structures are, and why they’re important in biology? Will we have to know this for the final?

Connor Ho 1B

I think doing the Marshmallow packet will help, as well as going over your midterm. If you have any previous notes from Chemistry classes from high school, maybe those will help as well.

Connor Ho 1B

No. The basic writing sequence is the same. Just remember that the Lewis acid-base reactions always have the same type of products.

Connor Ho 1B

In simple terms, the Bronsted acids and bases can be identified as such:
Acids give away H+ while bases accept H+.

Connor Ho 1B

I already have my grade in myUCLA, maybe if you check that

Connor Ho 1B

Cisplatin is used in chemotherapy to treat several cancers, including testicular cancer, ovarian cancer, cervical cancer, and breast cancer. Cisplatin damages DNA strands and inhibits the synthesis of DNA in order to halt growth of cancer cells.

Connor Ho 1B

In terms of Lewis acids and bases, determining which is acid and which is base is dependent on the chemical equation. More often than not, the lewis structure with hydrogen in it is the acid, and the other is the base. However, if there is no hydrogen in either, then the one receiving electrons is a...

Connor Ho 1B

To know whether these are basic, acidic, or amphoteric, remember that greater electronegativity means greater acidic character. For amphoteric compounds, remember that the elements around the division between metals and non-metals have amphoteric character. I've attached a photo to show this. https:...

Connor Ho 1B

In this question, we are asked for two things: 1) the desired pH 2) the actual pH For 1) pH is the concentration of hydrogen atoms in solution. Because the equation for HCL is the following: HCl --> H + + Cl - We can assume that since the concentration of HCl 0.025M, the concentration of H + is also...

Connor Ho 1B

Yes, it is true that linear structures have 180-degree bond angles, however, AX2E and AX2E2 have bent/angular molecular shapes. This shape is a result of the repulsion caused by the existence of the lone pair on the central atom. The repulsion is strong enough to make the attached atoms push away fr...

Connor Ho 1B

I believe the better lewis structure is the one that represents the S-O bonding as a double bond. This has a more realistic formal charge compared to the other structure.

Connor Ho 1B

Does the shape/arrangement of molecules affect its interactions with surrounding/other molecules? for example, does it affect bonding or bond strength, for that matter?

Connor Ho 1B

For trigonal planar shapes, all bond angles are 120 degrees.

Connor Ho 1B

The shape according to the VSEPR theorem is actually an angular (bent) shape, as it says in the solution manual, which is what gives the bond angle of a little less than 120 degrees. This is because in molecular shape, lone pairs do not appear in the final shape. However, in a Lewis structure, you w...

Connor Ho 1B

How often would you have to rearrange this equation to find other quantities? Should this be practiced? The rearrangment of this equation would be most likely to find the energy required to remove an electron, or finding the wavelength of a photon/electron. It should be practiced as I believe findi...

Connor Ho 1B

E = hv is used in general to find the energy of a photon, although it can also be interpreted to find the energy required to remove an electron. On the topic of quantum, E = hv is most likely going to be a major equation.

Connor Ho 1B

By knowing the orbital, it'll be easier to determine the number of valence electrons in an element, which are needed for bonding with other elements.

Connor Ho 1B

From my understanding, the Uncertainty principle basically explains that we cannot know the exact location or speed of an electron in an electron cloud. The wave function, however, helps to define the energy level (in the case of gen chem), like you said in the post. I don't believe the uncertainty ...

Connor Ho 1B

For me, studying is most effective when I'm in a quiet area (like The Study at Hedrick, lol) and I usually skim through the textbook lessons as well as the notes I take in class. I also look over some notes from my high school AP Chem notebook if any of the topics we learned are something I went ove...

Connor Ho 1B

Electron shells are defined by the energy level, n=1, n=2, n=3. Orbitals are the combination of details between the energy level and the "subshell" or the "shape" of the electron cloud. For example, an orbital is energy level + subshell, so 4d, 3s, 1s, 2s, etc. are all orbitals. ...

Connor Ho 1B

I asked him about this after class. From what I understand, until the 4s block is filled, the 3d block has a greater energy level. Once the 4d block is filled however, the 3d block then has lesser energy and you would fill in the 3d block as if it were normal. The reason behind this is the extremely...

Connor Ho 1B

Schrodinger's equation is basically meant to prove that there is no way to prove definitely where an electron is and how fast an electron is moving. In addition, the more you may know about one, leads to knowing less about the other detail. For example, if you do happen to know the speed of an elect...

Connor Ho 1B

Thank you so much for your advice! As an aspiring medical student, this gives me more inspiration to pursue my future as a doctor and look forward to my future education.

Connor Ho 1B

For the most part, the calculations are necessary in order to find the limiting reactant. However, it might be easier if you think of it this way: First, convert the grams to moles. This is necessary. Then, divide it by the coefficient in front of the corresponding element in the equation then multi...

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