CHEMISTRY COMMUNITY

bellaha4F

the constant is also on the constant sheet!

bellaha4F

an intermediate is seen in the product side first and disappears later, while a catalyst is added first to the reactant side and than reappears later on the product side.

bellaha4F

the most important thing to know about this is that it just means that the reactants sit on the surface of a catalyst rather than be absorbed, right? is there anything else we should know about adsorption?

bellaha4F

intermediates should not be listed in the rate laws, right? but rather replaced with the products that the intermediates depend on?

bellaha4F

for me, lyndon's review sessions are the best and most beneficial

bellaha4F

i don't quite understand what the variable "A" in the Arrhenius Equation means (k=Ae^-Ea/RT), can someone please explain it to me, thanks!!

bellaha4F

microscopic reversibility is when a reaction has the same intermediates (same pathway) in both the forward and reverse directions.

bellaha4F

i'm a little confused on the whole concept of electrolysis and electrolytic cells. can someone briefly summarize main points of what we should know?

bellaha4F

just to clarify, when using the formula Ecell=Ecathode-Eanode, when given the potential of one of the half reactions, we do NOT change the sign if its the backwards reaction right? So like if Cu 2+ + 2e --> Cu is +0.34 V, and the half reaction was Cu --> Cu 2+ + 2e, we would still use +0.34 V and no...

bellaha4F

are there any worksheets for preparation for test 2? thank you!!!

bellaha4F

can someone explain how a diamond is kinetically stable and thermodynamically unstable with respect to graphite?

bellaha4F

if a problem tells us to find the rate of a reaction, should we find the average rate or instantaneous rate? would the question specify it?

bellaha4F

i'm a little confused on how to find the top of your series in a redox reaction (ie the strongest oxidizing agent in reduction). can someone please explain, thank you!

bellaha4F

the galvanic cell will never have a negative Ecell right? because it's always a spontaneous reaction?

bellaha4F

should we always use platinum for our cell diagram if we are not given a solid metal in the reaction?

bellaha4F

the van't hoff equation (assuming that delta H and delta S are constant over all temperatures), calculates the equilibrium constant (K) at different temperatures.

bellaha4F

is the only thing we learned about salt bridges was that it allows ion transfer for the 2 solution to stay neutral? is there more information we need to know about salt bridges?

bellaha4F

halogens are usually -1, oxygen is -2 (with exceptions), hydrogen is -1, and pure elements are 0. you can also sometimes tell by the group/charge of the element.

bellaha4F

can someone explain to me the electron motor force and its significance?

bellaha4F

when using the gas constant for the gibbs free energy equation (delta G= -RTlnK), do you always use 8.314 J/mol.K?

bellaha4F

yes, and make sure to use the right gas constant for the units!

bellaha4F

would it be unitless since it is calculating K?

bellaha4F

both delta e and delta u represent the change in internal energy, and i think on the constant sheet it is also used interchangeably

bellaha4F

he never curves actual tests, however he changes the grading scale for the final grades. for example, if you get 50% of all the possible points in the course, you pass the class with a C-, and based on how everyone did this quarter, he will adjust the grading scale accordingly.

bellaha4F

it was PD TV HUGS. i don't remember what the actual words they came up with were haha

bellaha4F

Do we have to memorize any of the entropies' of substances, such as water or co2?

bellaha4F

the pizza rolls review worksheet that will be gone over tomorrow is based off of old test questions! i find that review session the most helpful

bellaha4F

1 L atm= 101.325 J is on the constant sheet for tests which can be found on the chem 14b home page!

bellaha4F

the boltzmann constant will always be given to us on tests right? thanks!

bellaha4F

so when calculating degeneracy, we also use Avogadro's constant when calculating the number of atoms right? so for example if there was only one mol of something, it would be the number of positions^(6.026 x 10^23)?

bellaha4F

can someone explain to me the difference between an irreversible and reversible path? thank you!

bellaha4F

can someone give examples of an isolated system?

bellaha4F

they were depictions of the different states the atoms can be in. all the microstates have the same energy!

bellaha4F

can someone explain the idea of kinetics please, thanks!

bellaha4F

will we need to memorize the heat capacity for different elements, or will it always be given on problems?

bellaha4F

^^to answer the conversion question, you would use 1 L*atm = 101.325 J conversion. it's on lavelle's constant and equations sheet!

bellaha4F

the tests are usually easier, with the questions kind of mirroring the homework problems. The midterm/final is much longer and contains complicated questions, from my experience last year.

bellaha4F

does anyone have the answers for the test 1 practice worksheet? thank you so much!!

bellaha4F

if all the components are gases, use kp. if all aqueous, use kc. (unless the test question says otherwise)

bellaha4F

10^-3

bellaha4F

is there a way to easily know what the polyprotic acids will break down into? i'm having trouble figuring out the reaction equations.

bellaha4F

can someone define what an inert gas is? and how to tell which gases are inert?

bellaha4F

can someone explain to me le chatelier's principle and how we use it, thanks!

bellaha4F

we won't need to draw lewis structures for reactions/products, or depict acids/bases on tests for 14b right?

bellaha4F

test 1 will be everything up until acids and bases!

bellaha4F

Hi, I'm a little confused on 5G9 and how to tell if certain amounts/etc. are going to stay the same or not. Can someone pls explain!

bellaha4F

If Q=K, the reaction is at equilibrium If Q>K, the reaction is at post-equilibrium. the reverse reaction will proceed because there's too much product or not enough reactants. If Q<K, the reaction is a pre-equilibrium. the forward reaction will proceed because not enough product has been made yet.

bellaha4F

My TA said if the reaction contains all gases, assume Kp. Otherwise, they would tell us in the directions of the problem to find Kc.

bellaha4F

can someone explain to me what an ice table is and how we use it?

bellaha4F

Q tells what point the reaction is at in relation to K, therefore it is solved the same way as K.

bellaha4F

When there's a solid or liquid in the reaction, I know we disregard it. Do we just substitute it with a one when writing the K constant?

bellaha4F

So in general a weak base will raise the pH and a weak acid will lower the pH, right?

bellaha4F

in the naming examples sheet on lavelle's website it says K3[CoF6] is potassium-hexa-fluoro-cobaltate(III). I was assuming the net charge of this is 0 because it doesn't say otherwise, so why is it cobaltate?

bellaha4F

i'm pretty sure after the sp
so for example: sp3d2

bellaha4F

polar, also none of the dipole moments can ever cancel out in T-shape if i'm not mistaken

bellaha4F

I think that was more chem 14b if I am not mistaken, and we don't really need to know that

bellaha4F

can anyone briefly explain hybridization and what we're going to need to know for the final about it?

bellaha4F

I don't understand why water is monodentate? I thought since there are two hydrogens attached to the oxygen molecule, it should be polydentate?

bellaha4F

i don't think so. we should just stick with what has been assigned for reading and homework and what dr. lavelle talks about in lecture!

bellaha4F

it's cumulative, based on everything we've learned starting from week 1

bellaha4F

this class has been very difficult for me, since I only took honors chem sophomore year of high school. it has been taking a while for me to get use to chemistry again :(

bellaha4F

if the net dipoles all cancel out (bc of electronegativities), then it will be nonpolar (if they all cancel out)

bellaha4F

I think that's it! As long as you can do the homework problems with that, you should be good.

bellaha4F

in one of the worksheet answer key it says that the boiling point of KCl is higher than KI. however I thought that since I is bigger than Cl, KI should have a higher boiling point?

bellaha4F

when the surface area increases, there's more room for temporary induced dipole interactions to occur, therefore more LDFs, therefore a higher boiling point.

bellaha4F

when the bond angle is less than what's normal (for example, bent with 2 lone pairs is less than 109.5), do we have to memorize the exact number (For example, water is 104.5)? Or is saying less than 109.5 fine?

bellaha4F

What is the difference between electron-pair geometry and molecular geometry? Should we know both or should we just know the molecular geometry?

bellaha4F

should we know hybridization for test 2?

bellaha4F

Is there ever going to be a case where a molecule could have 2 different VSEPR models?

bellaha4F

Knowing all of them will be the best I think, test-wise

bellaha4F

I think drawing the Lewis structure out first is helpful when determining the VESPR model, but I don't know if it's necessary. However, on tests, they might expect us to draw it out.

bellaha4F

I think going over outline 4 and doing all the homework problems would be a good way to study.

bellaha4F

I think we should know concept wise

bellaha4F

can someone explain what a coordinate covalent bond is?

bellaha4F

is the lewis acid and base valid for every single compound? or is it just some compounds that have a lewis acid and base?

bellaha4F

are there exceptions to the bond length rules (ie the triple bond is the shortest and strongest while the single bond is the longest and weakest)

bellaha4F

how do we calculate the dissociation energy? Is there a formula?

bellaha4F

I'm still confused on how to use the lyman and balmer series. Can someone please explain this to me?

bellaha4F

hi! can someone explain to me the expanded valence shell. i'm not sure I understand it completely!

bellaha4F

regarding the picture posted, I thought Cl has 7 valence electrons, and the chart says it has 5? I'm pretty sure that chlorine has 7 valence electrons? I could be wrong, unless I'm reading the picture wrong.

bellaha4F

how do you figure out the valence electron # of nonmetals/transition metals?

bellaha4F

electron affinity is the energy released when electrons are added to a gas phase atom. electronegativity is the electron pulling power of an atom.

bellaha4F

Do you think there's going to be different acceptable answers Lewis structure drawings on the midterm?

bellaha4F

should we know how to calculate the bond lengths of the lewis structures? is there even a way to do that?

bellaha4F

can someone explain to me the electrostatic/coulomb potential energy and its significance? I know it's proportional to (q1)(q2)/r.

bellaha4F

I think we should know it, and I'm assuming that it'd be really helpful for the tests!

bellaha4F

the ionization energies decrease down a group and increase across a period. however, it's only for gases

bellaha4F

Can someone explain what the Aufbau/building up principle is?

bellaha4F

quantum world probably because we only started the chemical bonds section, so some of it might not make sense

bellaha4F

when the frequency decreases, the amplitude of the wave also decreases and the wave becomes wider. the electrical field coincides with amplitude.

bellaha4F

I like to go through each homework problem and make sure I understand how to do every one of them! I also watch the modules.

bellaha4F

Will we have to know Schrodinger's wave function equation for future tests?

bellaha4F

aphung1G wrote:Does anyone know the energy of microwaves?

Arrange the following types of photons of electromagnetic
radiation in order of increasing energy: g -rays, visible light, ultraviolet radiation, microwaves, x-rays.

microwaves would have the least energy!

bellaha4F

What should we know about black bodies for upcoming tests?

bellaha4F

should we always show the percent yields in the limiting reactant problems, or just when it's specifically asked?

bellaha4F

We don't need a blue book! Good luck!

bellaha4F

should we draw diagrams for all the electron problems? Is it a necessity?

bellaha4F

for test 1, will we get points off if we round to the wrong significant figure?

bellaha4F

should we know the definitions verbatim of accuracy, precision, mole, etc. for the test?

bellaha4F

Can someone explain to me what exactly the avogadro number is and how we use it?

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