CHEMISTRY COMMUNITY

AdityaGuru1H

and if you are looking for which is most likely to be oxidized it would be the one with the lowest E

AdityaGuru1H

we use 3/2 when working with monoatomic molecule like Ne and constant volume and 5/2 for a monoatomic molecule constant pressure. Add 1 to both of them when using a diatomic molecule like H2. We don't need to know anything past monoatomic molecules on the test

AdityaGuru1H

i don't have the 7th edition but if a catalyst is introduced then the activation energy should be lower not higher

AdityaGuru1H

no in this case it would be because while step 2 may have been the determining step n2o2 was substituted by [no]^2 since n2o2 is not in the final equation. Only molecules that are in the overall reaction can be part of the rate law

AdityaGuru1H

from what i recall i don't think we can if we are given a random equation as the coeffeicents don't always line up with the order of the reaction so the only sure way to figure it out is through experimental data

AdityaGuru1H

it certain sense it is since in that we are trying to isolate the reactants to figure out each of their pseudo reaction orders independent of the other reactants

AdityaGuru1H

yeah it is just a way to balance out the delta concentration of reactants since it will be negative and we want it as a positive since the fact that reactants are used up is implied

AdityaGuru1H

to make sure that you don't confuse your signs it may be best to figure out which method you like the best and stick with that otherwise you may get wrong answers. A good way to check is to see if you get a positive answer as most of the cells should end up having a positive potential

AdityaGuru1H

There can basically be 3 situations The substance is thermodynamically stable so even over a very long period of time it will still stay the same under the same condition The substance is not thermodynamically stable but is kinetically so for the time period that we are worried about the substance w...

AdityaGuru1H

I think it is the just the maximum amount of work possible like how an isothermal expansion has more work than a constant pressure one

AdityaGuru1H

the salt bridge helps to prevent charges from being built up on one side of the cathode and anode interaction so that it can continue creating a current

AdityaGuru1H

you will use it when you want to know the K constant of a reaction at different temperatures when the standard enthalpy of formation is known

AdityaGuru1H

you will balance it like we have been doing it before(making sure the charges balance and matter stays the same), but you will use oxidation numbers to figure out where the charges change in the reaction

AdityaGuru1H

Also for most of the reactions you will want to use the change in moles of gases not of all substances

AdityaGuru1H

you can use it when t is constant and you can use deltaS=DeltaH/T when pressure is constant

AdityaGuru1H

how we measure if a system is open, closed, or isolated is if it is able to transfer heat or work with the surroundings which is also how we measure internal energy. In the case of an isolated system it is not able to transfer either so w and q are both 0 which makes deltaU = 0

AdityaGuru1H

Could someone please explain what we are supposed to do for #14 because I feel like i don't have enough information to do anything

AdityaGuru1H

For example work is not a state function because the work is different for a isothermal reversible reaction versus a non reversible one even though they both reach the same end points.

AdityaGuru1H

for this you will probably just have to assume since 25C is the temperature that the most stable state of a lot of molecules are at and 25C is the same as 298K. Sorry if this isn't much help

AdityaGuru1H

The last topic is basically all of what we went over today regarding entropy, i.e. system, surrounding and universal entropy. We won't need to do anything relating to gibbs free energy

AdityaGuru1H

I think constant volume is what you are trying to calculate for and in that case there would be no work done.

AdityaGuru1H

enthalpy is defined as the heat in the system so when we are talking about deltaH that is the change in enthalpy between a product and reactant. We can say that heat released is negative because we measure deltaH by products - reactants and if it is exothermic the heat of the product is less than re...

AdityaGuru1H

The other option would probably be using the standard enthalpy of formation method because the other method is only for combining the enthalpy of multiple reactions. On the test however the method that we use will probably be dertimned by what information we are given so i wouldn't worry too much ab...

AdityaGuru1H

basically it is the enthalpy required to form the product from reactants that are in their most stable state. Since the product is the most stable state the standard entalphy will be zero. It is a comparative value between the stable reactant and the product

AdityaGuru1H

If we are expected to do any polyphonic calculation then we should be give both ka1 and ka2 so that will tell you if you need to do any extra polyphonic calculations. If they don't give you two then you probably won't need to worry about it

AdityaGuru1H

if you look in the textbook the only acid that can even do this is H3PO4 but for that it is such a weak acid that the pKa is over 12 so we won't have to worry about that at all. The max we will have to go is Ka2 and that will probably be only if the first deprotanation is complete

AdityaGuru1H

that will give you the molar concentration of h30+ and you can do the same thing for 10^-pOH for the molar concentration of OH-

AdityaGuru1H

you basically have to memorize them. Feel free to correct me but I think the list is (there may be a few more bases but i am not 100% sure)
Acids: HCl, HBr, HI, HNO3, HClO3, HClO4, H2SO4
Bases: LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2

AdityaGuru1H

i think that the answer is c. This is because partial pressure can be derived from concentration using p= conc * r* t and so a decrease in partial pressure basically means that the amount of co2 is less so the reaction will go towards reactants and decrease the concentration of o2

AdityaGuru1H

from my understanding it is that you can't really define the concentration of lets a solid block of salt since the entire thing is pure salt, this can also be applied to any other solid. For liquids like water it is because the start and end concentration are so large and similar that it doesn't mat...

AdityaGuru1H

If i remember correctly from his videos we would disregard it if we were working with a cubic equation and if the k is less than 10^-4

AdityaGuru1H

basically since q is calculated the same way as k using conc[p]/conc[r], if q > k then that means that there is more product than there should be at equilibrium and the reaction will go towards the reactants and the reverse if q < k

AdityaGuru1H

We don't need to worry much about that since in his videos Lavelle said that we don't need to know anything about activity in undergrad

AdityaGuru1H

The way I did this was to simply assign the concentration a random number, I did a concentration of 1M and then do the calculation from there. It doesn't matter what value you use for the initial concentration. You would then calculate the pH of the concentration using -log(concentration). Then do t...

AdityaGuru1H

b would be the correct answer since the angle between the two NH2 would be in such a way that it could easily bond to two bonding regions of an octahedral Transition metal. A and C on the other hand have to great of an angle between the two NH2 for them to be able to easily bind to a transition meta...

AdityaGuru1H

I don't want to say 100% no but it would be highly unlikely as acidic rain occurs due to nonmetal oxides in the atmosphere such as CO2 and for basic rain to theoretically occur there would need to be basic oxides in the atmosphere which doesn't occur in large enough quantities to make the rain basic

AdityaGuru1H

A polydented is a ligand that can bond to the transition metal in multiple places. Usually it is the large molecule that are polydente but for the final since we don't need to know that many it may be easier just to memorize them. ethylenediamine and oxalate are bidentate diethelynetriamine is tride...

AdityaGuru1H

no for each set of hybrid orbitals all of the electrons are at the same energy level. For example for CH4 it is sp3 hybridized and has a total of 8 electrons. All eight of the electrons are at the same energy levels since there is new energy level that is in-between 2s and 2p and this allows all 4 o...

AdityaGuru1H

for the pi bonds you would have to imagine two balloons coming from the top and bottom of each atom and the adjacent balloons slightly overlapping each other. This is because the pi bonds use the p-orbital which are along the axis. Also because each p-orbital has two parts this explains why molecule...

AdityaGuru1H

so is the oxidation number basically the charge on the atom kind of like what the charge would be if the atom was an ion?

AdityaGuru1H

The formal charge on all 3 of the Boron is -1 but the formal charge on all 3 of the Nitrogen is +1 so when you add up all of the formal charges to get the total charge of the molecule you get zero. As such there is no need for a lone pair on any of the molecules so for both N and B the hybridization...

AdityaGuru1H

Since P has 3 different orbitals it depends if the orbitals from the two atoms are one of the ones that are parallel to each other, and thus have a weaker interaction making a pi bond, or if they or on the same line as each other, and have a much stronger interaction and make a sigma bond. it is imp...

AdityaGuru1H

yeah it should work since VSEPR is based off of the lewis structure so as long as we can get a lewis structure we should be able to use VSEPR

AdityaGuru1H

we will need to know only generic ones like octahedral is 90 degrees but nothing too specific like how NH3 is 107.5

AdityaGuru1H

This is because the overall structure if we include the lone pair is trigonal planar and in trigonal planar the bond angles are all 120 degrees. However this is if all 3 electron regions are bonding pairs, but in this case one of them is a lone pair which has more repulsion and will cause the bond a...

AdityaGuru1H

This is because the two electrons in the lone pair are held closer together to the single atom compared to a bonding pair which is split between two atoms. Since the lone pair is closer to the central atom they will have more repulsion

AdityaGuru1H

I am slightly confused about how dispersion forces work. Is it just based on the number of electrons that are able to be polarized and so the trend is just the more electrons the greater the dispersion or is there something else that I am missing?

AdityaGuru1H

Basically, with resonance structure the resonance bonds are basically a blend of the possible bonds since the electrons are more free to move around between the bonds and so due to some interaction that we don't really need to know too much about they will be something a little bit below the average...

AdityaGuru1H

the exception also applies to phosphorus so for the 3rd row it would be P<Si<S<Cl

AdityaGuru1H

For this the way to do it is to break it up into the 3 given sections H2C, NH2 and COOH and then from there combine the 3 parts. In situations like this it is important to note instances where the same element is repeated multiple times such as hydrogen being listed 3 times. This will usually give a...

AdityaGuru1H

By having more bonds(single double triple) the formal charge will increase as 2 electrons in a bond will take away 1 for the formal charge calculation while 2 paired electrons that are not in a bond will take away 2 from the formal charge valuation.

AdityaGuru1H

Also keep in mind that we are only doing the s and p block and only the first row of the d block so you won't have to remember anything too complicated

AdityaGuru1H

No you are correct, if you look on his website this is listed as a mistake in the solutions manual. To clarify +- 5 would be an uncertainty of 10. Hope this helps!

AdityaGuru1H

I am pretty sure I have heard both my TA and Professor Lavell say that we do not have to know schrodingers wave functions just n,l,ml

AdityaGuru1H

I was wondering why for the problem "In infrared spectroscopy, it is common to express energy in terms of frequency/c, with the units cm-1 (read as reciprocal centimeters). (a) If an absorption occurs in the infrared spectrum at 3600 cm -1, what is the frequency of radiation that corresponds to...

AdityaGuru1H

A nodal plane basically means that an electron cannot be on that plane so the density would decrease as we approached the nodal plane for each of the different orbitals. If we take the p orbitals for example, the point where the two lobes meet is a nodal plane and along that plane there is no chance...

AdityaGuru1H

The DeBroiglie Equation can be applied to anything that has a rest mass so it should be able to be applied to protons and neutrons

AdityaGuru1H

I don't think we have to know the exact reasons why for this class as we are not doing the math to come up with the plots for the orbitals. Im pretty sure as long as we know that it is on the xy axis that is enough and we may not even have to memorize that.

AdityaGuru1H

I was wondering if in this case could we use the Rydberg formula v=R{(1/(n1)^2)-(1/(n2)^2)}

AdityaGuru1H

Is the Rydberg constant (R= 3.29E15 Hz) something that we have to memorize like Avogadro's number for the tests?

AdityaGuru1H

I asked professor Lavell and he said that any molecular formula will be given and that we wouldn't need to determine the formula from the name

AdityaGuru1H

If we are not supposed to round until the end does it matter if we have the correct sig figs in each step of the problem or will the sig figs only matter at the end in regards to grading

AdityaGuru1H

for question E29 "A chemist measured out 8.61 g of copper(II) chloride tetrahydrate, CuCl2 4H2O. (a) How many moles of CuCl2 4H2O were measured out? (b) How many moles of Cl ions are present in the sample? (c) How many H2O molecules are present in the sample? (d) What fraction of the total mass...

AdityaGuru1H

From my best understanding a formula unit refers to a group of atoms that are bonded ionically while a molecule refers to a group of atoms that are bonded covalently, but please feel free to correct me as I am still not 100% sure of this myself

AdityaGuru1H

So if something has some prefix-hydrate does that always mean that there is a H20 attached?

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