CHEMISTRY COMMUNITY

Margaret Akey

So in a galvanic cell, whichever one is more positive, that means its more likely to be reduced and thus gains electrons (having e on the reactant side), and the more negative one is likely to be oxidized, and thus lose electrons (having e on the product side)? Yes, just make sure when you are look...

Margaret Akey

just another version of a derivation. they mean the same thing

Margaret Akey

zero order: rate = k first order: rate = k[A] second order: rate=k[A]^2 rate is always Molarity/second or Moles*Second^-1*Liters^-1 so when you have just rate = k for zero order.. Molarity/second needs to equal k, so k is Molarity/second (easy!) Now, when you have rate= k[A] for first order.. Molari...

Margaret Akey

reducing power is going to have more negative standard reduction potential oxidation power is going to have more positive standard reduction potential. the way i like to think about it is that since reduction power is the ability to give away electrons, the reduction half reaction that would not wan...

Margaret Akey

slow step is the one that matches the experimentally determined rate law

Margaret Akey

"The reaction mechanism describes the sequence of elementary reactions that must occur to go from reactants to products."
-khan academy
https://www.khanacademy.org/science/che ... mechanisms

Margaret Akey

The reaction rate does not increase from 0->2nd order... It doesnt really have a conceptual image. More like what patterns does the experimental data show with respect to concentration changes, and how can we represent these changes by raising the concentration's to a certain power to find a line of...

Margaret Akey

what is the difference between a chemical reaction and a reaction mechanism?

Margaret Akey

how do we tell if a reaction is zero order?

Margaret Akey

Lyndon's review sessions are good!

Margaret Akey

Just found a post from sometime ago by Chem_mod: "The Cl2 on the right side should be Cl-, it is a typo"

Margaret Akey

if you didnt have the inert metal there, how would the electrons transfer? they cannot just jump from an aqueous solution over to the other beaker..

Margaret Akey

I am confused about this too

Margaret Akey

same concept. porous disk only lets the spectator ions through, but everything is in one solution. salt bridge allows ion transfer between separate solutions. both salt bridge and porous disk have same function of keeping the solutions electrically neutral.

Margaret Akey

I also like watching the khan academy videos on the topics.

Margaret Akey

I have a feeling it is going to be extremely thermodynamics heavy. Like solve for deltaH and deltaS and then find gibbs free energy type of questions..

Margaret Akey

Ruiting Jia 4D wrote:Will acid/base consideration when balancing redox equations be on the test? It's in the textbook but not covered in lecture.

Yes. Its pretty simple because with bases its the same thing but you add an OH- on at the end.

Margaret Akey

kJ/mol

Margaret Akey

What is the purpose of the salt bridge?

Margaret Akey

how does gibbs free energy relate to redox and cell potentials?

Margaret Akey

how do you know which reaction is reduction and which is oxidation?

Margaret Akey

electrolytic: reduction in the left cell/electrode
galvanic: reduction in the right cell/electrode

Margaret Akey

One is a reduction reaction. One is a oxidation reaction. When put together=redox reaction!

I think you are talking about the salt bridge. It is necessary for ion flow so that the solutions are neutrally charged.

Margaret Akey

think about a fully charged battery, theoretically no current is flowing so it is max potential

Margaret Akey

delta H is change in enthalpy, delta U is change in internal energy

delta H is equal to delta U when there is no work going on, because PdeltaV is 0.

Margaret Akey

I dont think we need to know potential energy!

Margaret Akey

You can think about heat in the same way that you can think about how much energy you have to use while say, climbing a mountain. When climbing a mountain if you zig zag back and forth go back up and down the middle part of the mountain and waste a ton of energy, by the time you get to the top you w...

Margaret Akey

the biggest difference is that in solids and liquids there is no volume change!!

Margaret Akey

work will increase when heat increases because if you think about it... when you boil water you are providing heat in order to do work on the water to get it to boil

Margaret Akey

I always start with writing down all my givens. You can then look for formulas that can solve for what youre looking for.

Margaret Akey

For enthalpies, we can use in-between reaction enthalpies. for example: if we do not know A->C, but we do know A->B and then B->C. which would give us A->C

Margaret Akey

You have many different ways to find the solution to a problem! (you can go straight up the mountain, or you can zig zag all around it until you get to the top)

Margaret Akey

you can predict enthalpies with different information. i.e. if you are given different information to know which method to use in order to solve for the answer..

Margaret Akey

exothermic reactions tend to occur spontaneously (since energy is released), which makes ice melting/water boiling endothermic because you have to put heat in to have a phase change. it does not occur spontaneously (no energy is released)

Margaret Akey

do we have to look up the ka values ourselves in this case?

Margaret Akey

How do you know if it is a buffer reaction?

Margaret Akey

How do you know whether something is a conjugate acid or base?

Margaret Akey

Find the two reactions in the table, and when you add the two reactions together, the Cl- end up canceling. Then you are left with the correct chemical equation, and you take the two equilibrium constants and multiply them to get the equilibrium constant for the combined reaction.

Margaret Akey

Don't forget to balance your chemical equation!

Margaret Akey

always kelvin!

degrees celcius + 273.15 = kelvin

Margaret Akey

TRUE or FALSE:

(d) if one starts with higher concentrations of reactants, the equilibrium concentrations of the products will be larger

is this true or false, please explain if you can!

Margaret Akey

do we know how to write and reduce net ionic equations for the exam?

Margaret Akey

so the iron atom is tridentate?

Margaret Akey

how do you draw the ligand HN(CH2CH2NH2)2 and how do you know how many sites can bond simultaneously?

Margaret Akey

most stable structure is when middle atom's formal charge is 0 (Cl in this case)

Margaret Akey

CH4 is a C surrounded by all H's, so all of the H's pull the electrons from the carbon the same amount (i.e. nonpolar). In CH2Cl2, the Cl pulls much more on the Carbon's electrons (since it has higher electronegativity) than the Hydrogens, which sets up a dipole moment (i.e. polar).

Margaret Akey

Margaret Akey

how much s there is compared to p or d

more s character in sp hybridized orbital because its 50/50
compared to sp2 hybridized orbital which is 33% s
and sp3 is 25% s character

Margaret Akey

According to electronegativity trends, Cs has a lower electronegativity value than K, so the difference between Cs and Cl is greater than the EN difference between K and Cl. In this case though, the difference is so great that both KCl and CsCl will be ionic, with CsCl having greater ionic character...

Margaret Akey

1)whether it is a single, double or triple bond! 2) - single, double, then triple bond (in order from least dissociation energy to greatest) -smaller atomic radius = larger dissociation energy (and larger atomic radius = smaller dissociation energy) -lone pair presence tends to make bonds weaker (so...

Margaret Akey

not when you get lower down on the periodic table!

Margaret Akey

usually highly polarizable atoms/molecules have big electron clouds (so anions, large atoms/molecules with lots of electrons are highly polarizable)

Margaret Akey

the shape is trigonal pyramidal, so all bond angles are <109.5

Margaret Akey

boiling point and melting point both depend on intermolecular interactions

Margaret Akey

yes! and they are especially important for non-polar molecules since they dont have any other way of having an intermolecular interaction

Margaret Akey

why does butanol have a higher melting point than diethyl ether?

Margaret Akey

how do you know whether it has a rod or spherical shape?

Margaret Akey

what is a coordinate covalent bond?

Margaret Akey

How do you determine bond energy?

Margaret Akey

What is the difference between a sigma bond and a pi bond?

Margaret Akey

Can someone explain effective nuclear charge? Why does it go up as you go across the period?

Margaret Akey

First I draw the skeleton of the structure, with Cl in the middle, and the O's around the Cl. Then I count the total number of valence electrons (7+6*4+1=32 total) I draw in 4 single bonds between each of the O's and Cl, and then add in the lone pairs around the oxygens until everything has an octet...

Margaret Akey

I am curious about this question as well. I feel like it has something to do with having to have at least 1 electron in the n=4 level since its period is 4. If vanadium for example was [Ar]3d5, it wouldn't illustrate that Vanadium is N=4..

Margaret Akey

Do we need to know electron configurations for atoms with f orbitals for our Midterm, or just up to period 3?

Margaret Akey

or 3?

Margaret Akey

What about a 5p orbital? Would the degeneracy be 5?

Margaret Akey

Does anyone know of any worksheets or websites that has good practice for drawing lewis structures?

Margaret Akey

What are the main differences between ionic and covalent bonds?

Margaret Akey

What are the main differences between ionic and covalent bonds?

Margaret Akey

As this is the last topic we covered in class, correct? In the 7th edition, would this correspond with knowing the information up to section 1D, or does the test also include information from 1E?

Margaret Akey

Just know what the wave function is for, and the generals about it! No calculations (that is very difficult math :)

Margaret Akey

So the orbitals closer to the nucleus are always the ones that shield the further away electrons?

Margaret Akey

Pretty much always convert to meters, Joules, seconds, and be wary of kg/g. (You need kg when working with joules, but with conversions to moles you need grams).

Margaret Akey

Any wavelength greater than 10^-18 m is detectable, and therefore significant to us! A wavelength smaller than 10^-18 m is still technically a wave, but just is not significant enough for it to matter.

Margaret Akey

Think about ocean waves lining up together to create a big wave (amplifying), or lining up as to cancel each other out (destroying the wave).

Margaret Akey

I am still confused at how the Balmer/Lyman series were obtained, and what their significance is! I am having trouble wrapping my head around the atomic spectra. Any advice for how to visualize these concepts?

Margaret Akey

What do we need to know about SI Units for our first test?

Margaret Akey

There is a table method that works quite well, but I cannot remember how it works! Has anyone else heard of this?

Margaret Akey

There is a table method that works quite well, but I cannot remember how it works! Has anyone else heard of this?

Margaret Akey

When figuring out the empirical ratio, what happens if you divide by the smallest number, and it doesn't come to a clear solution like 1: 1.333 : 1 ? In the pre-assessment question number 19, the ratio was 1 : 2.38 : 1 ? How do you handle this?

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