CHEMISTRY COMMUNITY

AndreiRekesh1I

Heme complexes, myoglobin, and hemoglobin (and their function) may be important.

AndreiRekesh1I

Cisplatin in particular has 2 Cl on the same side, which allows it to bind to base pairs and stop DNA replication.

AndreiRekesh1I

For #1c on mini marshmallow, how do you know to choose NH4+ and not NO3- for the net ionic equation? Since they're both weak acids and bases H + NO3 becomes HNO3, which is a strong acid and would be more inclined to dissociate completely rather than be put together (the equation would make more sen...

AndreiRekesh1I

Hybridization usually comes in to explain when an atom has fewer valence electrons by nature than regions of electron density, like bonds and lone pairs.

AndreiRekesh1I

When the ligand is any kind of polydentate

AndreiRekesh1I

Lewis acids are electron acceptors and Lewis bases are electron donors. Bronsted acids are hydrogen ion donors and Bronsted bases are hydrogen ion acceptors.

AndreiRekesh1I

So far he hasn't gone over Arrhenius bases, and the homework problems don't seem to cover them either.

AndreiRekesh1I

When there are more than 2 atoms, there's usually an Oxygen in there somewhere, like HOBr, HOCl, etc. The ones that are more likely to dissociate depend on how much the non-O component of the anion (which would be Br and Cl in these cases) pull electrons towards it, which depends on electronegativit...

AndreiRekesh1I

Na[Fe(OH2)2(C2O4)2] - Since sodium is the cation, it is written in front, before the complex in brackets. Fe is the cation within the complex, so it's written before any ligands in the brackets. Water (referred to by diaqua) and oxalate (referred to by "bisoxalato", because the -o is added...

AndreiRekesh1I

I think Friday is a review day.

AndreiRekesh1I

Donor atoms are atoms that can donate an electron pair (so anything with a lone pair). The nitrogens in that molecule are likely the donor atoms because they have lone pairs.

AndreiRekesh1I

You can use london forces to compare boiling point if the molecules are both nonpolar, because then you know there's no dipole-dipole at play.

AndreiRekesh1I

Isomers are made up of the same atoms but completely different structures, but resonance doesn't mean there are multiple ways to structure the molecule (since the actual bond length and structure is just the average of the resonance structures).

AndreiRekesh1I

Then the atoms being compared are not bonded.

AndreiRekesh1I

There are fewer protons in its nucleus. Flourine also forms much stronger bonds with other atoms (which is one part of how electronegativity can be defined).

AndreiRekesh1I

Period 3, because that's when D-orbitals become available to accommodate extra electrons.

AndreiRekesh1I

If necessary we could probably reason that H2O has a smaller bond angle than NH3 because the O has two lone pairs, and the interactions between them are stronger than those between bonded atoms so they push the bonds further and squeeze the angle smaller.

AndreiRekesh1I

The names are kind of based on what the shapes look like (i.e. trigonal planar is a flat triangle "plane", and trigonal bipyramidal is two three-sided pyramids stacked base to base).

AndreiRekesh1I

It increases as you go left to right and up to down, because it increases depending on how many valence electrons there are and how far away they are from the nucleus.

AndreiRekesh1I

Induced dipole implies that it's being caused by another atom but instantaneous dipoles can happen just from the arrangement and movement of electrons around the nucleus (more on one side than the other at a certain point in time).

AndreiRekesh1I

They usually have more electrons so IMFs like dispersion are stronger. Also since electrons are further from the nucleus they can polarize more easily.

AndreiRekesh1I

It's the best way, but you could draw it specifically to focus on the arrangements of bonds and lone pairs on the center atom because that's what AXE tracks anyway.

AndreiRekesh1I

Typically the fewer electrons an atom needs to complete a full valence shell, the more electronegative it is.

AndreiRekesh1I

I am, I'm in the 3pm lecture if I can get the class

AndreiRekesh1I

They're not directly correlated but as electronegativity increases across the periodic table so do the number of protons in the nucleus so atom size goes down, as the protons attract the electrons more tightly. As we go down the periodic table, electronegativity decreases because electrons are furth...

AndreiRekesh1I

Dipole moment is how polar a bond between two atoms is. It's calculated by the magnitude of the charges of the two atoms multiplied by the distance between them.

AndreiRekesh1I

Coordinate covalent bonds are where both electrons in the bond are supplied by the same atom, sometimes represented by an arrow drawn from the donator to the receiver instead of a line for regular covalent bonds.

AndreiRekesh1I

I think doing all the problems he gives instead of a few probably gives a more complete picture of how the test will be, also reading over and understanding the bullet pointed concepts Lavelle outlined on his learning outcome sheets should help.

AndreiRekesh1I

I guess the other definition would be, if you don't know what the bond type is, it's determined by electronegativity difference between atoms (whether the bond has ionic or covalent character).

AndreiRekesh1I

It's the quality of ionic bonds to sometimes share electrons (usually because the anion is strong enough to pull electrons towards it), the way covalent bonds would.

AndreiRekesh1I

Since iodine is one of the elements that can break the Octet Rule, it's five chlorines around the iodine.

AndreiRekesh1I

IIRC l must be at most one fewer than n in all cases, and the absolute value of ml must be at most equal to l.

AndreiRekesh1I

When formal charge on atoms (usually the center atom is most important) is zero, then that configuration is the most stable.

AndreiRekesh1I

A formal charge of 0 generally means the atom is more stable because it compares the number of lone pairs and half the bonded electrons to the number of electrons the atom would have in its natural free state. Having that number be as close to zero as possible would mean that the atom in its bonded ...

AndreiRekesh1I

You can think of electronegativity as how "hungry" an atom is for electrons, usually because it wants to complete its outer valence shell. Since the furthest right elements of the periodic table are the noble gases, which are stable and already have completed valence shells, they aren't ve...

AndreiRekesh1I

This isn't true for all cases but usually resonance structures can be drawn whenever the diagram of a molecule has different types of bonds to a center atom whose locations are interchangeable. All the possible combinations of how these bonds can be arranged would be the number of resonance structur...

AndreiRekesh1I

The difference in electronegativity (or at least the absolute value) between atoms in a compound provides a rough measure of its polarity. This helps differentiate between nonpolar covalent, polar covalent, and ionic bonds.

AndreiRekesh1I

Ionization energy is the energy required to remove an electron from a single atom, but threshold energy refers to the amount of energy required to remove an electron from a metal surface via light (like in the photoelectric effect).

AndreiRekesh1I

Hydrogen only has one electron, I think it's the interactions between electrons that cause these differences in energy levels.

AndreiRekesh1I

I think the second equation you're referring to is the definition of momentum, the first one is related to indeterminacy

AndreiRekesh1I

I got the same answer; I assume it's a typo because it's not even the unit the problem is asking for.

AndreiRekesh1I

If the object isn't some sort of electromagnetic radiation you can't really assume it travels at the speed of light and find the frequency that way.

AndreiRekesh1I

Will we not be able to know our "participation" grade for posting on this website until the end of the quarter or are there updates?

AndreiRekesh1I

I'm curious to see how lenient the graders are with partial credit

AndreiRekesh1I

Wavelength is inversely proportional to energy, so shorter wavelength (represented by lambda) would have enough energy to eject e- from a metal while a higher wavelength might not.

AndreiRekesh1I

Wavelength is inversely proportional to energy, as wavelength decreases energy increases.

AndreiRekesh1I

In my experience, remembering not only the values of constants but also the molar masses of common elements saves a lot of time.

AndreiRekesh1I

It's best to use them only in your final answer, otherwise rounding at each step may cause your final answer to be less accurate. The final answer will also be the only one where graders actually care about the correct number of sigfigs.

AndreiRekesh1I

serenabirkhoff_1K wrote:I understand it is 5 problems each week but how is it graded? Is it completely by accuracy?

I don't think they're graded by accuracy, at least that's what my TA said

AndreiRekesh1I

Often in labs you can know how accurate your results are by comparing the experimental values to theoretical ones, and how precise they are by repeating the same experiment multiple times and comparing the results to one another.

AndreiRekesh1I

For combustion reactions in particular, I find that balancing oxygen last is easiest.

AndreiRekesh1I

It's probably best to use the number of sig figs in the givens.

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