CHEMISTRY COMMUNITY

pamcoronel1H

Thank you!

pamcoronel1H

I'm not completely sure on this, but I think it's because E(nought) by definition is the STANDARD reduction potential that gives the voltage difference of two electrodes. Since it gives you the voltage difference, this makes E(nought) an intensive property and therefore doesn't change no matter how ...

pamcoronel1H

You can know if work is done by looking at the equation, deltaG=-nFE. If deltaG is negative, this means that E MUST be positive and that the system has to be doing work since its losing energy.

pamcoronel1H

1 line indicates that the two substances are in contact with each other, while 2 lines indicates theres a salt bridge separating each side from the other. For example, in: Cu | Cu2+ || Fe3+, Fe2+ | Pt(s) Cu and Cu2+ are reacting with each other, while (Cu and Cu2+) and (Fe3+, Fe2+ and Pt+) are separ...

pamcoronel1H

Could someone explain for 4a how he got 5.0x10^3?? When I worked it out on my own I got -498 and all my elements cancelled out.

pamcoronel1H

An elements most stable form is usually is usually its more "basic" form. For example, O2 has a deltaH of 0 since it's only using one element. Another example would be that C(gr)--> C(gr) is in its most stable form since it doesn't take any energy to remain in the same state, but C(gr)--> ...

pamcoronel1H

The formula you would use is w^n, where w is the number of possible states for the system, and n is the number of atoms. This equation shows us through the n exponent that degeneracy strongly depends on the number of atoms rather than the possible states.

pamcoronel1H

I am having a bit of trouble with the quadratic equation in this question. I got the quadratic equation of x^2+0.3x-0.06, but when I put this into the quadratic equation, I get a negative number in the square root part (sqrt(-.15)) and I can't take the square root of that. Anyone know what to do in ...

pamcoronel1H

Does anyone know if Test 1 solutions will be posted? I was just wondering since I want to use Test 1 as a practice test for the midterm.

Thanks!

pamcoronel1H

The standard enthalpy of formation is defined by the enthalpy per mole of formula units of a reaction with STABLE elements.

So, for example, O2 is made up of O and O, which is a stable reaction and so its a "null reaction".

pamcoronel1H

No, a closed system can still exchange energy with its surroundings while an isolated system cannot. Using examples Professor Lavelle gave, an example of a closed system would be a beaker with a seal on top, so no matter can be exchanged but the surroundings can still interact with the outside of th...

pamcoronel1H

Just to clarify, was the reason why steam causes severe burns was because as vapor turns to liquid it releases more a lot of heat (40.7 kJ). Or is there more detail behind this?

pamcoronel1H

Hi!

Could someone explain why the work function is not a state function. I understand it is because you need to know the "pathway", but what is this pathway and why cant' it be added or subtracted to see the change in work?

Thanks!

pamcoronel1H

I am confused about the pattern of strength described in the solution. In my lecture notes I have it that the stronger the acid, the weaker it conjugate base, so that would be that a higher pKa would mean a lower kb and therefore a weaker conjugate base, right? The solutions manual says that the str...

pamcoronel1H

If you increase the pressure, the reaction will favor the side with the fewer moles because since the volume available now is decreased, the reaction will want to take up the least space possible. For example, in: 2 O3 --> 3 O2 If you increase the pressure here, the reaction will tend to favor the r...

pamcoronel1H

When we worked through the example of how does increasing pressure affect the reaction, I was a bit confused by the results. For the initial concencetration, Q for the reaction N2 + 3H2 --> 2NH3 was found to be 100, and for when pressure was doubled, Q was found to be 25. From this, how do we know t...

pamcoronel1H

If Q<K, that means that K is bigger and there is a higher value on the numerator of the k equation, i.e. there's more products at equilibrium than what we currently have. So, the reaction will need to proceed forward in order to get the amount of product that is favorable in equilibrium. If Q>K, tha...

pamcoronel1H

Since we're trying to find the CHANGE in concenctrations of the living and dead tissue, you just subtract the two concentrations: (7.214 x 10^-11 mol.L-1) - 8.435 x 10^-3 mol.L-1, and you should get -8.43499993 x 10^-3.

pamcoronel1H

From what I got from the textbook, it says that the higher electronegativity of an atom, the stronger the acid. Cl has a higher electronegativity than H, and so it is the stronger acid.

pamcoronel1H

I'm not sure if this is the answer to your question, but I believe that the complex shape depends on the number of ligands rather than the TM. A coordination compound with 4 ligands can therefore have a square planar complex because of the 4 regions of electron density.

pamcoronel1H

The central atom for CNO should be C, since it has the lowest ionization energy. The Lewis Structure should then have one covalent bond between C and O, and 3 covalent bonds between C and N. Also, O has 6 lone pair electrons and N has 1. When you calculate the formal charges, the FC of C is 0, the F...

pamcoronel1H

They're both interchangeable. Since ionization energy is the energy needed to remove an electron, that means that an atom with a high ionization energy will also have a high electron affinity since it really wants to keep or get electrons.

pamcoronel1H

If C and O were double bonded, the FC of C would be -2 and the FC of O would be 0, adding up to a total charge of -2. When C and O are triple bonded however, the FC of C is -1 and the FC of O is 1, which add up to a charge of 0, which is a more stable structure.

pamcoronel1H

Hi!

Does anybody know how to calculate the oxidation number when naming a coordination compound?
Professor Lavelle said that for [Fe(CN)₆]^-4, it has an oxidation number of 2(II), but I am lost as to how he got to this number.

Thank you in advance!

pamcoronel1H

I beleive it's just 90 degrees.

pamcoronel1H

London forces should apply here so I'm not sure why the manual says that. London forces although weak, are present between any two molecules.

pamcoronel1H

The reason for writing the electrong configurations is that it helps you visualize which orbitals are being shared, since its usually the electrons in the outermost orbitals that interact with other atoms. Professor Lavelle also mentioned that the number of regions of electron density= the number of...

pamcoronel1H

I believe it's because they have a tendency to want to lose electrons in order to hace an octet and be more stable. So, that would mean they are more likely to transfer electrons to another atom.

pamcoronel1H

To add on, a sigma bond has no nodal planes while a pi bond has one nodal plane.

pamcoronel1H

Hello,

I was doing the homework for the hybridization section for the textbook and was having trouble getting what the questions were asking. Can someone explain to me how do you find the hybrid orbitals for molecules, such as in question 4.35?

Thanks!

pamcoronel1H

A sigma bond is basically when the outermost orbitals of 2 atoms overlap. A sigma bond has no nodal planes, i.e. the electrons can be found anywhere around the internuclear axis since both orbitals are overlapping each other. https://www.google.com/url?sa=i&source=images&cd=&cad=rja&...

pamcoronel1H

If a nonpolar rod-shaped molecule is interacting with another nonpolar rod-shaped molecule, they are more likely to find areas of attraction by London forces because their shape allows them to have multiple points of contact. A spherical molecule on the other hand, has less points of contact with an...

pamcoronel1H

This is usually determined by looking at which atom in the molecule is more electronegative. For example, H2O is a polar molecule because the Oxygen is more electronegative, i.e. the electrons are more drawn towards the oxygen atom. This is because elelectronegativity is based on the atoms ionizatio...

pamcoronel1H

I believe formal charge is more important since, if its an ion, the formal charges of your Lewis structures have to match the ionization of the molecule. Also, when making your Lewis structure, you usually want a structure with a minimal amount of total charge. This means that the formal charge affe...

pamcoronel1H

It is basically saying 2 things: One is that in any orbital, no more than 2 electrons can be held at that orbital. The second thing is that if there are 2 electrons in the same orbital, they HAVE to have paired spins, i.e. one is spinning in a clockwise direction and the other in a counterclockwise ...

pamcoronel1H

Since it is h/mv, and J=kg×m^2 the units are:
(kg×m^2)×s/kg×(m×s)
The kg, s, and one m cancel out, leaving only one m on top, which is your unit for wavelength :)

pamcoronel1H

You can use the following formula to find the number of orbitals: ml=2l+1. Since l=1, the number or orbitals that can have that quantum number is 3.

You can also do it without the formula. Since we know l=1, we know that it is a p-orbital, and a p-orbital always has 3 orbitals.

pamcoronel1H

Thank you so much for the thorough reply!

pamcoronel1H

Hello everyone!

I couldn't make it to Wednesday's lecture this week, so I was wondering if anyone could share the topics we went over or even their notes from Wednesday, I would greatly appreciate it :)

pamcoronel1H

I believe that the part about the lower energy levels is shown on the solutions manual, but ultimately I think this whole thing about the energy level is what leads to the series being categorized as they are,i.e. that the Balmer series is in the visible light region and the Lyman series in the UV r...

pamcoronel1H

Although it is a lot easier to use Rydberg's equation, I would think that it would be best to do it the way Professor Lavelle taught us, so that would be using the En=(-h)R/n^2 and $\Delta$
E=Efinal-Einital equations.

pamcoronel1H

If you get a negative value when calculating the Energy difference, then that means that the electrons went from a higher energy level(n) to a lower energy level(n) and therefore are losing energy. If they're losing energy, that would mean that the atom will EMIT light.

pamcoronel1H

Diffraction patterns are a result of interacting waves, meaning they mainly come from the constructive intereference of waves i.e when waves are "in phase", which is when their peaks and troughs line up with each other. As the textbook explains it, it says that a bright line appears on the...

pamcoronel1H

In the beginning, it was observed that when electrons were passed through a crystal, a diffraction pattern could be seen, just like how light-that we know has wavelike properties- also shows diffraction patterns. This meant that electrons have both particle-like and wavelike properties. Quantum mech...

pamcoronel1H

I think it's best to always convert to L first , since the units for molarity is always mol·L^-1.

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