CHEMISTRY COMMUNITY

Kyle Alves 3K

also, if it wasn't given that the cell is galvanic, you can determine anode and cathode by:
reversing the half reaction with the lower E as that is more likely to be oxidized - will be the anode
the higher E will be reduced - will be the cathode

Kyle Alves 3K

I would think about the pbolem like this:
Ni => Ni^(2+) + 2e- which is therefore the oxidizing anode
2H^(+) + 2e- => H2 which is therefore the reducing cathode

The oxidizing agent reduces: so H+/H2
The reducing agent oxidizes: Ni2+/Ni

Kyle Alves 3K

Does anyone know any jokes about sodium? Na. Yeah, I know that was sodium funny!

Kyle Alves 3K

How did the chemist survive the famine?

He subsisted on titrations.

Kyle Alves 3K

Why do chemists enjoy working with ammonia? Because it's pretty basic stuff.

Kyle Alves 3K

Hey are you nervous for your basketball game Diamond? -No, I do good under pressure, and when the situation gets hot, it doesn’t phase me.

Kyle Alves 3K

Heisenberg is rushing home in his car. He gets pulled over and the officer approaches his car. “Sir,” he says, “do you know how fast you were going?” Heisenberg replies “No, I do not, but I know exactly where I am.”

Kyle Alves 3K

why do chemists call helium, curium, and barium the healing elements? Because if you can’t helium or curium, you barium!

Kyle Alves 3K

Hey Chemistry Cat! Tell us a potassium joke! Chemistry Cat: “K”

Kyle Alves 3K

You don’t want to mess with Helium, take away his electrons and he’ll threaten to cause cancer, and he isn’t bluffing.

Kyle Alves 3K

Why did the white bear dissolve in water? Because it was a polar bear.

Kyle Alves 3K

Little Willie was a chemist. Little Willie is no more. What he thought was H2O was H2SO4.

Kyle Alves 3K

I must be an exothermic reaction because I'm running out of energy.

Kyle Alves 3K

yo momma so ugly not even fluorine would bond w her.

Kyle Alves 3K

Did you know that you can lower your body temperature to -273 °C and be perfectly 0K?

Kyle Alves 3K

In a sports relay race, a chemical kinetics specialist runs slowly, and his group loses the race.

When the chemical kinetics specialist is asked why he ran slowly, his reply was “I always wanted to be the significant rate determining step”.

Kyle Alves 3K

Can someone explain why a reaction with a very negative standard reduction potential is a powerful reducing agent, and vice versa? Thanks!

Kyle Alves 3K

We then set for your question the forward and revers rates equal! This is to study individual orders. if want to study the forward rate, we would put B and C in large excess and input exponents (N,M,L) k[A]^N [B]^M [C]^L = k'[A]^N the A concentration will cancel out and leave you with: k = k'/([B]^M...

Kyle Alves 3K

From Lavelle's Lecture of 3/5 we need to be able to differentiate the rate constants between a forward and reverse rate for example, a second order reaction would be A + B => C + D the forward rate= k[A][B] C + D => A + B the reverse rate = k'[C][D] at equilibrium(forward = reverse rate) k/k' = K

Kyle Alves 3K

Did anyone get the correct answer for the other form? It did it the same way as this problem in corrections, but wanted to make sure they're both the same. Thanks!

Kyle Alves 3K

You can also solve for the units of k for each order! Since rate always begins with mol/(L.s)
Zero order(mol/L.s) = k[A mol/L]^0
mol/(L.s) = k

First order (mol/L.s) = k[A mol/L]
/s = k[A]

Second order (mol/L.s) = k[A mol/L]^2
(mol/(L.s)) = k[A]^2 (mol^2/L^2)
L/(mol.s) = k[A]^2

Kyle Alves 3K

Refers to calculating K at different temperatures
At T1: lnK1 = -(deltaH/RT1) + (deltaS/R)
At T2: ln K2 = -(deltaH/RT2) + (deltaS/R)

leading to
lnK2 - lnK1 = ln(K2/K1) = -(deltaH/R)(1/T2 - 1/T1)
just factoring the negative into the temperature will switch the two

Kyle Alves 3K

Since W = microstates^(# of particles), multiple resonance structures have many different microstates. Yeah drawing them out really helps!

Kyle Alves 3K

I think the only case it would show up is if we know both the Hvapor and Hsolid, which would make Hsublimation = Hvapor - H solid
and in all cases its endothermic and a positive value!

Kyle Alves 3K

The easy way to remember is:
an extensive property is energy/temperature, only depends on amount of substance (heat capacity is in kJ/K which is like q/T)
an intensive property is energy/(temperature x amount), which is like kJ/(C x g) for specific heat or J/(K x mol) for heat capacity

Kyle Alves 3K

I don't know where I went wrong with this problem, would be helpful to see what other people did!
Calc K for the following redox rxn: Sn^(2+) + Pb => Pb^(2+) + Sn

And is the reaction spontaneous? Thanks!

Kyle Alves 3K

Could someone explain why we would need to know the molecularity of the equation in the context of a problem? Is it only to determine rate law?

Kyle Alves 3K

In all of Lavelle's lectures it was always k is the forward reaction and k' is for the reverse! I don't think he would change that for the final

Kyle Alves 3K

I know this has been answered on the other test, but it would be really helpful! The question asks to calculate the standard potential for the following reaction using the reduction potentials on the last page of the test: Fe^(3+)(aq) + 3e- => Fe(s) If anyone got this question right and could share,...

Kyle Alves 3K

Can anyone answer how we could tell without being given the standard reduction potentials? I had the same question, and I know a high E is good at oxidizing and a lower E is good at reducing. This was a question on test 2 q 5

Kyle Alves 3K

Quick question I'm confused on:
If we want 400g of water at 16 C, how many g of water at 25 C and g of ice at 0 C do you need? I think we set the heats opposite each other, and use mCAT, but Im getting negative numbers.

Kyle Alves 3K

Also in an equation solving with weak acids and bases, its set up either: for a weak acid: HA + H2O = H3O+ + A- where A is the shorthand for acid, to solve for Ka, or the acidity constant for a weak base: A- + H2O = OH- + HA where A is the shorthand for base, to solve for Kb, or the basicity constan...

Kyle Alves 3K

It might be one of those "you should just know" pieces of information: SiO2 can't exist as a molecule by itself, Si has to be connected to two other oxygens atoms to make a covalent network, rather than just being a molecule by itself. Although it makes a nonpolar molecule overall, the SiO...

Kyle Alves 3K

For pH of a strong acid, you can assume it is 100% ionized and then put it straight into the pH calculations = -log[H30+], but for a weak acid you have to calculate the Ka (acidity constant) to find the pKa. The lower the pKa the more acidic. Hope it helps!

Kyle Alves 3K

Probably a simpler example because the last one is confusing:
between HCl and HBr, Cl is more electronegative so pulls in e- greater, making the bond stronger
therefore, HBr would e a stronger acid as it is less stable with its longer bond length

Kyle Alves 3K

electronegativity can also be seen as in making the conjugate base more stable and therefore showing it is a stronger acid. For example: between HIO and HIO3, HIO3 is a stronger acid with a more stable conjugate base as the e- charge is more equally dispersed between 3 Os than one O. The more disper...

Kyle Alves 3K

I think the point of the explanation of nodes was only to show the e- distribution of atoms (e.g. s orbitals have no nodal plane so it has symmetric e- distribution), and that might help in explaining something on the final

Kyle Alves 3K

Basically for problems it helps most to write out the ground state of an element first following aufbau and the other principles. If any representation doesn't follow the principles (e.g. a pair of e- have an ms of +1/2 in an orbital), then it is excited

Kyle Alves 3K

I'm confused why a square pyramidal structure like IF5 wouldn't have resonance, can anyone explain?

Kyle Alves 3K

I looked at one of the previous answers to test q 4, and it generally made sense that a dipole moment must have all the e- neg atoms on one side for there to be a dipole moment, but wouldn't PO4^3- have one if all the oxygens with a negative charge are on one side and the double bonded oxygen on ano...

Kyle Alves 3K

To expand, Lavelle went over it in his lecture on 11/1, and the equation looked like this:

u = qr

u being the dipole moment in debyes
q being the separate charges
and r being the distance between atoms

Kyle Alves 3K

To clarify, we don't calculate a Ka or Kb because we assume for strong acids and bases are 100% ionized in a solution, because the equilibrium concentration otherwise is so small it becomes useless in calculations. That would mean that for example: 0.1M HCL would 100% ionize to form 0.1M H3O+ and 0....

Kyle Alves 3K

For clarity, the autoporalisis of H2O given for Kw is usually set at 25 degrees C, so if the temperature is to change, the equilibrium of the reaction will change as well to compensate Kw = [H3O+][OH-] = 10^(-14) the last post explains what happens, this is just the equation to supplement. hope it h...

Kyle Alves 3K

Also, the easiest way to remember is if the elements in question are part of the metalloid oxides section of the periodic table
as opposed to the nonmetal oxides (group p) which are acidic and the metal oxides (group 1 and 2) that are basic

Kyle Alves 3K

Lavelle also provided a good example in his past lecture of relative acidity!
Cl - O - H
Br - O - H
I - O -H

Since Cl is so electronegative, it stabilizes the negatively charged O by drawing in e- density, making it more acidic than I - O - H

Kyle Alves 3K

I'm having some confusion over what happens when amplitude changes! I know amplitude is the height of waves, but I'm confused when that changes how it affects wavelength and frequency. Wouldn't it make sense if the height of the waves increased, that the frequency of the waves would increase as well...

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