CHEMISTRY COMMUNITY

Artin Allahverdian 2H

Thanks, that makes sense

Artin Allahverdian 2H

What is termolecular?

Artin Allahverdian 2H

How would we know when exactly to use the Arrhenius equation?

Artin Allahverdian 2H

Rust is when iron is exposed to water, causing Fe to oxidize into Fe2+. Water acts as the oxidizing agent for Fe so the dissolved ions present in water are what get reduced. The more dissolved ions in water, the faster rust happens.

Artin Allahverdian 2H

It is more a question of whether the process itself is reversible. The problem will usually tell u if it is reversible or irreversible. If it is reversible, deltaS of the system will equal the negative of deltaS of surroundings. Work itself is based on if the rxn is isothermal, in which deltaU is 0 ...

Artin Allahverdian 2H

If we are given the acid and it’s pKa, but we want to solve for the pH of its base, do we need to convert pKa to pKb?

Artin Allahverdian 2H

To clarify if Q>K the reaction would want to shift in the reverse way to make more reactants in order to reach K. Since this will make the reverse rxn more favorable than the forward rxn, the forward rxn will not be spontaneous, and thus, delta G is 0.

Artin Allahverdian 2H

Greater than 0 because it will be non spontaneous

Artin Allahverdian 2H

How do we know when to include the ions playing a part in the reaction, but that don’t get oxidized or reduced, such as H+, OH-, or any other ion into the cell diagram?

Artin Allahverdian 2H

Why does the solutions manual throw in KOH into the anode portion of the cell diagram when K plays no part of the reaction??

Artin Allahverdian 2H

Ok so I have no idea what is going on with this redox reaction. It doesn’t look like any species is oxidized or reduced, and I’m having trouble following the solutions manual when it balances the half reactions. Can someone please explain this one?

Artin Allahverdian 2H

Why are the units of k different between different reaction orders ?

Artin Allahverdian 2H

What would be an example of a zero order reaction? I’m having some trouble understanding what it means conceptually.

Artin Allahverdian 2H

What is meant by the "unique" rate of a reaction?

Artin Allahverdian 2H

Why do we mostly just focus on the initial reaction rates as opposed to the rate later in the reaction?

Artin Allahverdian 2H

What is the difference between E and E naught?

Artin Allahverdian 2H

What exactly does the reaction order mean?

Artin Allahverdian 2H

How do we know when delta U is zero given the context of a problem?

Artin Allahverdian 2H

How do you know when to use deltaS=nRln(T2/T1) versus deltaS=nCln(T2/T1) whenever a gas goes through a temperature change?

Artin Allahverdian 2H

Why does a higher heat capacity mean a less steep slope?

Artin Allahverdian 2H

What exactly is meant by a “reversible” process or an “irreversible” process in the context of thermodynamics?

Artin Allahverdian 2H

When calculating q for an ideal monatomic gas with the equation q=nCdeltaT, how do we know when to use 5R/2 versus 3R/2 for C?

Artin Allahverdian 2H

kb (the Boltzmann constant) is equal to R (the gas constant) divided by Avogadro’s number. Basically, this relates the energy level for each particle.

Artin Allahverdian 2H

What exactly is the difference between an isothermal reaction and a non isothermal reaction?

Artin Allahverdian 2H · Re: Friday 02/01/2019 lecture artallahverd@gmail.com

artallahverd@gmail.com

Artin Allahverdian 2H

Hello, I was absent for the Friday 02/01/2019 lecture and was wondering if anyone could share the notes of what we learned in lecture that day. Thanks!

Artin Allahverdian 2H

I am kind of confused as to what constitutes a state property. Can someone give an example explaining what does and doesn't constitute a state property? Thanks!

Artin Allahverdian 2H

Although a phase change does not change in temperature, energy is still inputted into the system in order to break the inter-molecular forces between molecules. There is much more energy required for a phase change from a liquid to gas than there is for a phase change from solid to liquid, so when y...

Artin Allahverdian 2H

I believe if we come out with any concentration for H3O+ that is smaller than 10^-7 we should still consider it as slightly acidic but very close to neutral since we know that autoprotolysis generates 10^-7 mol/L of H3O+, so it wouldnt make sense of our H3O+ concentration was less than that. If we d...

Artin Allahverdian 2H

For #12, why does an increase in pressure on the system not cause a shift in neither the reactants nor products side?

Artin Allahverdian 2H

U can solve for pH given the pOH given the following equation:

pH+pOH=14.
pH=14-pOH

When u solve for pH then u can find the molarity of the substance using this equation:

-log[concentration of substance]=pH
concentration of substance=10^(-pH)

Artin Allahverdian 2H

Why does a change in temperature result in a change in the equilibrium constant for a reaction? Is temperature the only thing that can alter the equilibrium constant or are there other variables that can affect it as well?

Artin Allahverdian 2H

First, remember that Q=[products]/[reactants] at an instantaneous given time not at equilibrium. So when Q<K, it indicates that there is a higher concentration of reactants in the denominator than for the ratio for K, thus resulting in a smaller number for Q. Since we want the reaction to proceed to...

Artin Allahverdian 2H

Can someone explain why we have to multiply the 2 K values together when combining the 2 separate reactions together as opposed to adding them?

Artin Allahverdian 2H

Lets say we have a chemical reaction at equilibrium where one of products/reactants is a gas and another one of the products/reactants is aqueous. When calculating the equilibrium constant for a specific case like this, would we just use the concentration of the aqueous reactant/product and the part...

Artin Allahverdian 2H

How would we be able to tell if a given acid/base is strong or weak?

Artin Allahverdian 2H

In this question why can the nitrogens accept protons, but not the oxygens? In general, how can we tell if an atom/molecule can accept a proton or not?

Artin Allahverdian 2H

How can we tell if a ligand is polydentate so that we know whether to use bis-, tris-, tetrakis-, etc?

Artin Allahverdian 2H

Why is Ka1>Ka2>Ka3?

Artin Allahverdian 2H

Oh I almost forgot. Since the resonance bonds are longer than a double bond but shorter than a single bond, they will be stronger than a single bond, but weaker than a double bond, since bond length is inversely proportional to bond strength.

Artin Allahverdian 2H

Say you have a resonance molecule that has 3 bonding pairs and 2 are single bonds and one is a double bond. However, we can move around that double bond to the other bonding pair positions to form 3 resonance structures. In the real world, the bonds of resonance structures are the average of the res...

Artin Allahverdian 2H

If a conplex ion has 2 nobmetals in it, how do we know which one we name first? For example in [Co(NH3)5(SO4)]+, which nonmetal will we name first?

Artin Allahverdian 2H

What causes oxoacids to be stronger acids if the atom that O is bonded to is more electronegative?

Artin Allahverdian 2H

Dr. Lavelle refers to bases as having a “soapy” feel. Why is it exactly that causes bases to feel this way and what is its significance?

Artin Allahverdian 2H

Are we supposed to know how to calculate pH for acids and bases? If so, how is it calculated?

Artin Allahverdian 2H

-ate is added as a suffix to the transition metal if the whole ligand itself has an overall negative charge.

Artin Allahverdian 2H

I think that’s just how it is because it makes turning the compound into a single, long word easier that way than having the metal name come first.

Artin Allahverdian 2H

The NO2 Lewis structure has a central N atom that is double bonded to one oxygen and single bonded to another oxygen. Since this molecule has an odd number of valence electrons (17), it is a free radical, in which N will have a lone, unpaired electron. This unpaired electron acts as a lone pair, pus...

Artin Allahverdian 2H

If you look at the Lewis structure of this molecule, a central S atom is bonded to 3 O atoms. Each S-O bond is a double bond, and S has no lone pairs. Thus, S has 3 regions of electron density (a double bond counts as a single region of electron density, and there are 3 of them, hence 3 regions of e...

Artin Allahverdian 2H

Why is it that we can ingest vinegar, but if it is poured into a cut, it hurts?

Artin Allahverdian 2H

Can someone please review how ionic bonds can have covalent character and how certain cations can form ionic bonds with more polarizing power and thus more covalent character?

Artin Allahverdian 2H

Can someone please explain why chelating compounds can form multiple bonds with the same metal, and why just any other coordination compound cannot do the same?

Artin Allahverdian 2H

Can someone please explain 2F5 letters b and c (7th edition) in the homework? I am having a hard time understanding the whole hybridization concept, so I’d be quite grateful if someone could summarize it for me. Thanks!

Artin Allahverdian 2H · Re: Last Friday 11/09/18 lecture artallahverd@gmail.com

artallahverd@gmail.com

Artin Allahverdian 2H

Does anyone have the notes for last Friday’s lecture? Thanks.

Artin Allahverdian 2H

Hello, I missed the lecture today due to traveling for athletics and I was wondering if someone could provide me with the notes. I would also appreciate if someone can send me a link to the bruincast video for this lecture (if it exists). Thanks!

Artin Allahverdian 2H

Great thanks!

Artin Allahverdian 2H

I think for a question like this he would have to give you the electronegativity values just because it is hard to decipher the electronegativity comparisons just by looking at the periodic trends.

Artin Allahverdian 2H

Why is CF4 more ionic than CH4? To me it seems that the electronegativity difference is more between C and H than between C and F just because H is farther from C than F is. Is there something else that I didn’t put into account?

Artin Allahverdian 2H

In this question it says that the emission of energy leads to the spectral line at 102.6 nm for the wavelength. If there is an emission of energy, then doesn’t that mean that the energy goes from a higher energy level to an lower energy level? If that is the case, then why does the answer say that t...

Artin Allahverdian 2H

So remember how in covalent bonds the electrons aren't shared perfectly equally so one atom is slightly positive and the other is slightly negative? Is the atom that is slightly more negative the one that is more electronegative?

Artin Allahverdian 2H

I don't have that answer to that, but id like to know why as well

Artin Allahverdian 2H

For the easy structures u will not have to do much work since there are no exceptions. However for resonance, u can tell because the molecule will be the same just with the double bond occurring in either side. Calculate the formal charge just to make sure it is resonance. For the free radical eleme...

Artin Allahverdian 2H

Can someone please explain why the electron configuration for Cu2+ is [Ar]3d^9 and not [Ar]3d^8 4s^1? Thanks!

Artin Allahverdian 2H

Hello, I was absent for Friday’s lecture and I was wondering if anyone could give me a thorough recap of what Dr. Lavelle talked about. Thanks!

Artin Allahverdian 2H

The Pauli Exclusion Principle states that there can be no more than 2 electrons per orbital. For an orbital that has the full amount of 2 electrons, they must be spin paired, meaning one spins up while the other spins down. Hunds rules states that electrons in the same sub shell occupy different orb...

Artin Allahverdian 2H

I also forgot that u asked about frequency. If frequency increases then wavelength decreases since wavelength*frequency=the speed of light, where the speed of light is a constant. Thus, if frequency decreases the wavelength increases. Now that you know what happened to wavelength, then you can use t...

Artin Allahverdian 2H

If the indeterminacy in wavelength increases, then the indeterminacy in momentum will decrease since by the de Broglie relationship (wavelength=h/p) wavelength and momentum are inversely proportional to each other. Thus, if the indeterminacy in momentum decreases, then the indeterminacy in position ...

Artin Allahverdian 2H

*To clarify I meant why does chromium like it’s 3d orbitals half full while copper likes it to be completely full?

Artin Allahverdian 2H

Why is it that the exception elements Chromium and Copper take an electron from the 4s orbital and toss it into the 3d orbital? I know it is because they don’t want to have the 5th 3d orbital to be empty, since they like all of them to be half full, but I guess the extent of my question goes to why ...

Artin Allahverdian 2H

@ bonnie_schmitz_3K

Actually, 3d comes before 4s, given that 4s is fully occupied, because 3d has a lower energy state than 4s.

Artin Allahverdian 2H

What exactly is it that causes an s-electron to have lower energy than a p-electron in the same shell?

Artin Allahverdian 2H

If an electron jumping to higher energy levels indicates that there is more positive energy, then why is the value for E sub n in the Rydberg equation still a negative value?

Artin Allahverdian 2H

We learned about the Schrodinger wave function. We can use a wave function Ψ (psi) to describe an electron with wavelike properties and indeterminacy in position and momentum. Ψ represents the height of the wave @ position x, y, z. Ψ^2 represents the probability of finding an electron. the wave func...

Artin Allahverdian 2H

I'd say you are right on. Perhaps to add a little more, the Schrodinger equation we are learning about, H(psi)=E(psi), is time independent. The time-independent equation considers the electron's quantum state to not be changing, and thus considers the electron to be a standing wave. Also, to be put ...

Artin Allahverdian 2H

Can someone please explain how we write the subshell notation and the number of orbitals, given the quantum numbers n, l, and/or m?

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