CHEMISTRY COMMUNITY

Dong Hyun Lee 4E

Both the foward and the reverse reaction should be altered by a use of a catalyst. Try going foward and going backwards on the graph.

Dong Hyun Lee 4E

The catalyst will be in both the reactants of the first step as well as the products given in the last step. However intermediates are created between the first and the last step and are not present in the final products.

Dong Hyun Lee 4E

Catalysts increasethe rate of reactions as they lower the activation energy required to pass the transition state.

Dong Hyun Lee 4E

Yes the slowest rate is the rate controlling step because it acts as a bottleneck where the rate cannot go any faster than what is limited as it controls the reaction rate.

Dong Hyun Lee 4E

Both reactions are important but the slowest reaction is the bottleneck of the reaction and thus determines the rate of the reaction itself.

Dong Hyun Lee 4E

How do you determine the slowest step then? is it the lowest k value?

Dong Hyun Lee 4E

The slowest step determines the fastest rate that the reaction can go because the slowest step limits the reaction rate.

Dong Hyun Lee 4E

What would be an example of the 1st and 2nd order then? I understand that the sums are different but I don't understand how to get the values to begin with.

Dong Hyun Lee 4E

This is because for later reactions we need to take into account the reverse reaction rate also which causes this to be more complicated.

Dong Hyun Lee 4E

I think the overall sum is the sum of all the exponents

Dong Hyun Lee 4E

This is because when you end up with products, some of those products might go do the reverse reaction causing trying to find the rate more difficullt

Dong Hyun Lee 4E

How do you tell the difference of the first and second order reactions?

Dong Hyun Lee 4E

Lavelle has a few calculus tips on his website. I doubt he will make us do difficult calc problems but probably just basic ones

Dong Hyun Lee 4E

I'm confused on which equation is used in which situation as I know most of the textbook questions use the equation (change in g= change in h - t * change in s) so when do we use G= -RT ln(k)?

Dong Hyun Lee 4E

If I remember right, Lavelle said it doesn't matter but just to be safe I think putting the one with the highest oxidation number in the middle would be better. I'm not a hundred percent clear tho. Can someone go ask Lavelle or a TA?

Dong Hyun Lee 4E

The anode equation shouild be flipped because you would have to look at the reverse reaction. Think of which way the equation is written down.

Dong Hyun Lee 4E

Platinum shouldn't be added to the overall equation because it is a inert conductor hence it doesn't effect the reaction.

Dong Hyun Lee 4E

An example of where K=0 would be the example he went over in class where when T=333K, BR2 was in both liquid and gas phase. This was called the boiling point. And when T was above 333K, the reaction favored foward and when T<333K a reverse reaction was favored.

Dong Hyun Lee 4E

There is no more "free energy" to do work because the reaction is at equilibrium and so a foward nor a backwards process is favored. Think about a ball in a valley, if the ball is on an incline, it will roll down. However if the ball is at equilibirum or the lowest point of the valley, the...

Dong Hyun Lee 4E

Boilin gpoint is when liquid and gas phase coexist so for the example he used would be when T=333k. If T>333K, then a foward process is favored as it was gas phas eonly and the change in s term dominates. And if T<333K then a reverse process is wanted as it is liquid phase only and the change in h t...

Dong Hyun Lee 4E

You probably won't but it isn't a bad idea to know it as deriving the equation can make it a bit easier to understand what is going on.

Dong Hyun Lee 4E

It will probably be on everything we learned after the midterm until test 2. Meaning Gibbs to however far we get in electrochem.

Dong Hyun Lee 4E

A larger/more comlex molecule has higher entropy because there are more bonds in the system which lead to more disoreder or entropy.

Dong Hyun Lee 4E

Yes if there is no mention of a pressure change, it is usually safe the assume that the pressure is being kept constant.

Dong Hyun Lee 4E

The more complicated a molecule, the higher the entropy because the range of motion that the parts may be in is larger. Using this logic, gasses have the higest entropy, then liquids and then solids.

Dong Hyun Lee 4E

We will do calculations around a calorimeter but I don't think we will need to know how to actually use one. I would check with your TA or Lavelle during this week to make sure.

Dong Hyun Lee 4E

An open system allows anything to pass into the system while a closed system only allows energy (so like a thermometer). An isolated system is a system is completely isolated from outside energy and matter.

Dong Hyun Lee 4E

The temperature of the water doesnt change but when it becomes steam, the extra energy due to phase change results in a more severe burn

Dong Hyun Lee 4E

Inert gases dont react with any of the reactants. However inert gases do change the pressure but since this is not due to volume, the reaction doesnt change.

Dong Hyun Lee 4E

The direction of a reaction can change due to a change in volume (pressure). Using Le Chatleier principle, the equation will favor whatever side has less moles

Dong Hyun Lee 4E

Inert gas doesnt react with any of the reactants but it changes the pressure. However, the pressure is not a change of volume so it ends up not affecting the reaction.

Dong Hyun Lee 4E

K is the equilibrium constant so it doesnt really change as it is based on when the equation is at equilibrium. However Q is not a constant and is when the reaction is not at equilirbium. Hence Q should be the only one that changes.

Dong Hyun Lee 4E

A catalyst can only speed up the foward or reverse reaction and thus it doesn't really change the reaction itself.

Dong Hyun Lee 4E

You will have to choose between bars vs molarity depending on the information given to you in the problem. If it is in bars then you use bars and vice versa.

Dong Hyun Lee 4E

If you think of the reaction as a factory producing a product, an equilibrium for a factory is that the number of items built and broken down into parts again would leave the "equation" at a certain ratio. So when the factory gives away all its products or NH3 in the case of this equation....

Dong Hyun Lee 4E

Kp will not use units as when calculating Kp with units you can see that the top and bottom units cancel out leaving only a number as the final answer.

Dong Hyun Lee 4E

Calculating Q and K are the same. Q is just when the equation is not at equilibrium so you compare that value to K in order to figure out which direction the reaction is going. To calculate Q or K you need to do products over reactants.

Dong Hyun Lee 4E

The acid would lose the proton (H+) and create a conjugate base. while the base would gain the proton and become the conjugate acid.

Dong Hyun Lee 4E

I think you have to memmorize the strong acids and weak acids and the strong and weak bases also for right now. The equations we will be solving out will only include that of strong as they disassociate completely or almost completely. For acids, it is stronger if the bond between the two elements i...

Dong Hyun Lee 4E

A neutral ligand would include H2O NH3 NO CO NH2CH2NH2 NH2CH2CH2NHCH2CH2NH2. all of these would not affect the charge of the cordination compound. Theses are also under how to name coordination compounds on Lavelle's website

Dong Hyun Lee 4E

What are the rules to naming conjugated compounds and what are some easy to follow examples?

Dong Hyun Lee 4E

I understand that amphoteric compounds can act as both bases and acids but how do we figure out when it acts as which. Is it that one part of the chemical equation will be an aid so the amphoteric compound would result in a base or how would this work?

Dong Hyun Lee 4E

So is the only way you can identify an acid and a base is either through how it is written out or by receiving the actual chemical equation to see what bonds and products are created?

Dong Hyun Lee 4E

When you draw out the different orbitals (S,P,D,F) for different atoms, thhe orbitals will overlap with each other. Since the s orbitals would overlap horizontally, they would be considered overlapping end to end, while the p orbitals which reach out vertically from the atom would interact side by s...

Dong Hyun Lee 4E

Any bond will be considered as a single electron region as it acts like one region together. Just because it is a triple or double bond does not make the bond act as three or two different electron regions.

Dong Hyun Lee 4E

I think it has to do more with the number of bonds. So a single bond is a sigma bond, a double is a sigma and pi bond, and a triple is one sigma and two pi bonds. . Yes the number of bonds are important but more the reasoning behind why these bonds are done like this as when visualizing the differe...

Dong Hyun Lee 4E

The most important thing to remember is that the electrons are repelling each other and wan to be as far from each other as three dimensions will allow them to be. So whatever number of atoms you have just arrange them so that they are the largest angle apart from each other as possible. As for the...

Dong Hyun Lee 4E

No because lone pairs would effect what the shape of the molecule would be. It would be both the number of bonds that are around the central atom as well as the number of lone pairs on the centeral atom.

Dong Hyun Lee 4E

What is the meaning of the solid line or the dotted line on Lewis Structures that are 3D? So I did some research on what the different types of bond drawings were and what they meant. A solid line means that the bonds are on the same plane as the paper. A dashed line means that the bond extends awa...

Dong Hyun Lee 4E

Bases give lone piars and acids receive lone pairs. Basces usually cotain NH3, F-, -OH and acids usually contain BF3, H+.

Dong Hyun Lee 4E

You want to first make sure that you have the total number of valence electrons of all elements in that compound and at least one bond per connected element. When that is done, you want to make sure every element fits the octet rule (except the exceptions) and then check for the least ammount of for...

Dong Hyun Lee 4E

The most stable configuration is when the formal charges for all elements of that compound are zero or closest to zero. Formal charge is the number you get when you subtract the number of bonds and lone pair electrons from the valence electrons of an element. If you have a positive formal charge nex...

Dong Hyun Lee 4E

No there is not a specific order to how you should do your lewis dot structure but go around once to put 1 electron on each side and then keep going around depending on how many electrons you have to mark.

Dong Hyun Lee 4E

Most atoms want to follow the octet rule (except for a few like H) but think of 8 being like the "most stable state" and hence you will need to fill it up to move to the next orbital.

Dong Hyun Lee 4E

To be safe lines should probably be only used as bonds and dots if the electrons are not being shared. Only use shortcut methods when the professor verbally says it will be ok to do so.

Dong Hyun Lee 4E

I think of electronegativity as how strong the pull of the atom is on the electrons while I see ionization energy as the amount of energy needed to displace a electron from an atom.

Dong Hyun Lee 4E

H bar just stands for h/2pi. He does have the equation given on the first page of the exams but I would memmorize the equation he has taught us in the class where (indeterminancy in momentum) times (indeterminancy in position) = h/(4pi). As this is just easier to memmorize and use. It is useful to k...

Dong Hyun Lee 4E

From what I understand by reading, the different series have idfferent principal or (like base level) enery levels. So for the Lyman seires, the lower energy level is n = 1 and for Balmer it would be n=2 and so on and so on.

Dong Hyun Lee 4E

Reading the textbook would not be a bad idea however for this test, I would focus more on the topics we have covered on the test as well as the practice problems we have been assigned so far.

Dong Hyun Lee 4E

If i remember correctly, Lavelle stated that he would not make us draw the different orbitals. But I would memmorize the number of lobes and planes they do have as S is spherical and does not have a nodal plane. P orbitals have 2 lobes on either side and a nodal plane. D has 44 lobes and etc.

Dong Hyun Lee 4E

Using the equation v = c / lambda where lambda = the wavelength. When wavelength is shorter v is greater (as for UV lights) and using the second equation of E = hv, v being greater would result in more energy.

Dong Hyun Lee 4E

It should be in joules per atom

Dong Hyun Lee 4E

An angstrom is just another unit name for 10^10 meters. So use this if your answer is in meters and is above this amount for a reasonable unit. It's like measuring a road as you would'nt give the distance in centimeters unless specifically asked to for a 4000 m stretch of road.

Dong Hyun Lee 4E

The smallest detectable wavelength that we can get is 10^-18 because this is somewhat similar to Angstroms which are 10^-10. However anything smaller than this wavelength will be hard if not impossible to detect and it would be too small to be of any importance and that point. I'm going to guess tha...

Dong Hyun Lee 4E

I think what Professor Lavelle meant by the car having non-wavelength properties was that the car's wavelength was 10^-34 and so he would consider it to be safe the wavelength was around 10^-10 or an angstrom. This would make sense because anything much smaller than this would result it in having su...

Dong Hyun Lee 4E

When trying to balance equations, you might run into numbers that are decimals. To turn these into whole numbers, you will want to multiply something that will result in all the coefficients becoming whole. As an example in class when left with a coefficient like 1.33, multiplying by 3 will land you...

Dong Hyun Lee 4E

Adding onto the question above. I understand how the answer would come out but using the SI measurements, would it be incorrect to leave the answer in meters and not kilometers. And if it would be incorrect could someone explain to me why that would be the case?

Dong Hyun Lee 4E

So when given a balanced equation and told to find a limiting reagent, you will most likely be given how many grams or how much of some element or compound you will start out with. So a simple example of this would be that the balanced equation of making hotdogs is 1 dog + 1 hotdog bun = 1 hotdog. S...

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