CHEMISTRY COMMUNITY

Rida Ismail 2E

Hey can someone tell me what we are supposed to use as the temperature. Is it assumed that it is 298K? Also how is n=1 and not 2?

Rida Ismail 2E

Can someone please help me on end of focus problem 25 25. Vision depends on the protein rhodopsin, which absorbs light in the retina of the eye in a reaction in which one form, metarhodopsin I, is converted to another, metarhodopsin II. The half-life of this reaction in cattle eyes in 600microsecond...

Rida Ismail 2E

The units are s-1

Rida Ismail 2E

Does anyone understand how an overall order can be negative and if so can you please explain it to me?

Rida Ismail 2E

How would you get an overall order of 3/2? This is displayed possible in one of the thinking points in focus 7A.3 in the textbook. Also in that case what are the units of an overall order of 3/2?

Rida Ismail 2E

Maya Pakulski 1D wrote:How would we determine what the intermediate reaction is if we are not given it?

I think it has to be given

Rida Ismail 2E

I don't think there is a way for you to see which is the slow equation. I think they have to give it to you.

Rida Ismail 2E

My guess is there will probably be an online alternative. I'm sure that Dr. Lavelle will send out an email in the next few hours about what he is going to do about finals.

Rida Ismail 2E

Gosh I was wondering this as well. I think that the review sessions will probably have an online alternative.

Rida Ismail 2E

In order to solve this problem, you need to see which choice gives you an answer that has the smallest delta S. A would be the answer because that is the only one in which the state stays solid throughout, and solids have the lowest entropy values.

Rida Ismail 2E

The questions on the final usually are not all from the homework. Some of them will be made up, but you should be able to bank on the fact that some will be from past homework problems.

Rida Ismail 2E

I thought that elementary equations were the only ones where they determine the order of the reactants in the rate law.

Rida Ismail 2E

I think the water is always one of the half reactions. It will give you an element and given the ox number you look it up in the back of the book (appendix 2B). Then figure our which is reduced and which is oxidized from the Ecell standard.

Rida Ismail 2E

I looked on the reduction potential list and found the one with Tin corresponding to the ox number given in Sn(NO3)2. Then you also get the hydrogen reduction potential on the list too. Figure out which is reduced and which is oxidized and then find the standard Ecell.

Rida Ismail 2E

Yes I and Pb should be separated by commas

Rida Ismail 2E

Can someone explain the idea of overpotential in the context of why they would need to reduce the overpotential in order to increase efficiency electrolytic processes?

Rida Ismail 2E

Can someone please help me with part a. I don’t understand how ozone is being reduced. Balance each of the following skeletal equations by using oxidation and reduction have reactions. All the reactions take place in basic solution. Identify the oxidizing agent and reducing agent in each reaction. a...

Rida Ismail 2E

I think it is positive just by the rules of kinetics. The forward reaction is always positive while the backward reaction is negative. Think of them as opposites and the forward reaction was made the standard. The backward reaction is negative because it is the opposite of the standard.

Rida Ismail 2E

I got the same answer as you. I am going to try to go to an office hour to ask this question, but my guess is that the book is wrong.

Rida Ismail 2E

if there is the word standard before anything, it is referring to the standard conditions that must be met (1M, 1 atm, and 25 degrees Celcius)

Rida Ismail 2E

This method is used when you want to calculate the entropy of vaporization for a value other than the known or given. In this case, the temp we want to find is at 85 degrees Celcius. So we need to bring up the temp to 100, use the known entropy of vaporization of 100-degree Celcius, and then cool it...

Rida Ismail 2E

entropy is the same in both scenarios because entropy is a state function. It doesn't matter what path you take to get the change in entropy, it will be the same.

Rida Ismail 2E

The different delta S are determined by the circumstance you are in. If you are addressing the system then that is DeltaS of the system. If you want to know the change in entropy of what is surrounding the system, that is DeltaS of the surroundings, and the DeltaS total is adding the DeltaS of the s...

Rida Ismail 2E

The change is delta G needs to be negative

Rida Ismail 2E

delta G is the most forward way to determine if the reaction is spontaneous or not.

Rida Ismail 2E

yes the second law is applied to irreversible situations because entropy is a state function.

Rida Ismail 2E

The reducing agent is what oxidizes
the oxidizing agent is what reduces

Rida Ismail 2E

for a basic solution you need to be sure to include the H2O and H+, but with acidic solutions you only add the H+

Rida Ismail 2E

The anode is on the left and the cathode is on the right. This is the correct way to do it. I don't think I've ever seen it the other way, but I'm not completely sure. It may be a different convention for different cells that we haven't learned.

Rida Ismail 2E

I think it depends on the energy of the element. Like in some cases there are different levels of energy lost by the electron, so it can become possibly semi-stable when it loses just 1 or 2 electrons. This way there are the oxidation states of -1 and -2. I'm not completely sure though.

Rida Ismail 2E

The way I study is reading over the notes, read the book, do ALL the homework problems, and make sure to ask questions on everything you are confused on because Dr. Lavelle can ask questions on virtually anything out of those options.

Rida Ismail 2E

For Dr. Lavelle's test 2 last quarter there were 10 questions. I would say it's safe to assume between 8-10 questions

Rida Ismail 2E

I thought the positive and negative relate to spontaneity. Like if it is positive the reduction is spontaneous.

Rida Ismail 2E

There’s two ways to figure this out. If the total entropy is positive then it is spontaneous. Also if the total Gibbs free energy is negative then it is also spontaneous. It is easier to tell spontaneity from gibbs free energy because it does not require us to know the entropy of the surroundings an...

Rida Ismail 2E

For a Hess’s law equation anything you do to the chemical equation you need to do to the Delta H as well

Rida Ismail 2E

This equation will probably be the only way that he asked us to calculate degeneracy. Also the amount of micro states will be given and from that we calculate W

Rida Ismail 2E

There are several gas constant to choose from but you should always choose the one that allows you to have all the units cancel. Ensure that you do not introduce new units with your gas constant

Rida Ismail 2E

The Boltzmann equation strictly talks about the residual entropy that is relating to degeneracy in disorder. The W represents the amount of micro states raise to the power of the number of particles. The Kb is the Boltzmann constant

Rida Ismail 2E

An extensive property means that it depends on the amount of the substance and an intensive property means that it is independent of the amount of substance

Rida Ismail 2E

We don’t have class that day but there is a review session

Rida Ismail 2E

Cv is strictly for constant volume and Cp is for constant pressure.

Rida Ismail 2E

Can someone explain to me why there is a delta in front of the H and not the S? Dr. Lavelle spoke about this today but I still didn’t quite grasp the information.

Rida Ismail 2E

I would looks at the parts of the bomb calorimeter in the notes and study how the parts work together (and the purpose that each part serves$

Rida Ismail 2E

U is the internal energy so delta u would be the change in internal energy

Rida Ismail 2E

Both are correct. It depends on what the problem give you.

Rida Ismail 2E

The plateaus are places of phase change while the positive slope areas is where temperature is increasingly the system.

Rida Ismail 2E

It is comparing reversible to irreversible. Reversible is able to act as work several times as small perturbations can cause work to be done. With irreversible reactions the work is a tied upon once. Also if you look at the equations, the equation to calculate the w for reversible has more variables...

Rida Ismail 2E

Usually it will state the temperature. If not there should be some indication that the system is at STPbin that case you can assume 25 degrees Celsius. STP basically means standard temp and pressure and standard pressure is roughly 298K.

Rida Ismail 2E

I agree with that. Significant figures for add and subtract only come from the decimal. If there is none there then when you calculate make sure ur answer has no decimal as well. It would not be correct to make it two sig figs because that would cut the number off in the hundreds place and that is n...

Rida Ismail 2E

The R is equivalent. It just depends on what units Lavelle will give us in a problem. Bases on the units we can determine with to use.

Rida Ismail 2E

Well it is very important to know because you want to see what is naturally exchanged. In open both matter and energy is exchanged. In closed just energy is exchanged. And in isolated nothing is. The type of system definitely affects what stays constant.

Rida Ismail 2E

all gases interact with each other in the real world making them non-ideal. But some are very close to a ideal which makes the ideal gas law a good approximation.

Rida Ismail 2E

its delta T so no you don't if the temperature is given in Celcius. Of course, you will have to convert to either C or K if it is in F. But the scale of C and K are the same making the delta T the same.

Rida Ismail 2E

The temperature stays the same because the energy going into the system is used to change the phase of the substance and not increase the temperature. Once the phase change is complete the temperature starts rising again.

Rida Ismail 2E

I was having a bit of the same problem where I felt like I wasn't 100% sure how to do the problems. I'm not sure if he briefly went over it in class and I must have not understood it fully or if he is going to go back at a later date. I actually just read the chapter and it explained it pretty well,...

Rida Ismail 2E

Does anyone who was in Lavelle's 14A class last quarter know when and where we can pick up our past 14A final?

Rida Ismail 2E

I think the easiest way is to check how many you had in quarter 1 and then subtract that from what you have now.

Rida Ismail 2E

I think the easiest way is to check how many you had in quarter 1 and then subtract that from what you have now.

Rida Ismail 2E

Diana A 2L wrote:What is considered an inert gas? Do we have to remember a list of them or is there a way to tell if a gas is inert?

and inert gas is a gas that has 8 valence electrons. So they are on the rightmost column of the periodic table.

Rida Ismail 2E

no, you just need to make sure that you are differentiating between products and reactants. products are on the numerator and reactants in the denominator

Rida Ismail 2E

Can someone explain to me what Dr. Lavelle was explaining in class about the true reason why increasing pressure goes to the side with fewer moles of gas?

Rida Ismail 2E

Kc is used when you have the molarity of a solution. Kp is always used with gases.

Rida Ismail 2E

K is strictly for when the equation is at equilibrium. If it is not at equilibrium then the constant Q is used but they are calculated the same way. Maybe comparisons can then be made about K through the values of Q surrounding it.

Rida Ismail 2E

I remembered that when the pressure was increased it moved to the side with fewer moles because if there is more pressure, the gas wants more area to spread out. If there are fewer moles with more pressure the moles of gas are not as cramped.

Rida Ismail 2E

In high school, I remembered exothermic to be related to the word exterior, so the heat comes to the outside and is, therefore, is released to the exterior of the system. Endothermic is the opposite.

Rida Ismail 2E

I thought that this only applies only to gaseous reactions. I am not 100% though.

Rida Ismail 2E

the higher the K, the more the products are favored. If the K is extremely large, theoretically there would not be a backward reaction because only the forward reaction is favored.

Rida Ismail 2E

I like to get into a study group and go over key concepts that are addressed throughout the year. I also make flashcards to ensure I know the concepts

Rida Ismail 2E

You leave positive or neutral names of the metal the same.

Rida Ismail 2E

Does anyone understand how to do the problem where it asked if the structure was in the Neutral for Ionized form due to the pH and the Ka values on the final?

Rida Ismail 2E

It was neutral due to the strong acid and strong base reacting in the neutralization reaction

Rida Ismail 2E

Dr. Lavelle, Thank you so much for teaching me all that you have this year. I have learned so much and have gotten a much better understanding of Chemistry through this course than I have with any high school course I have taken. You are so clear and through with your lectures and exams. I absolutel...

Rida Ismail 2E

From what I calculated. I got acidic for the first one and basic for the second, based on the fact that HCl is a strong acid and Ba(OH)2 was a strong base. So the H+ and OH- would dissociate and make the solution acidic and basic respectively.

Rida Ismail 2E

How does the pH of water change when temperature increases and decreases?

Rida Ismail 2E

The metalloids are amphotermic. They can act as both to lose and gain a proton.

Rida Ismail 2E

I heard from past students that the midterm was worse than the final.

Rida Ismail 2E

I believe Dr. Lavelle calculates chem community. I think you should do it 5pts a week. But if you miss a week I think you can make it up the following week.

Rida Ismail 2E

As long as you thoughtless cover all the outlines you should be okay. Study the homework and book (and obviously notes) to determine the exact knowledge you will be tested on.

Rida Ismail 2E

As long as you thoughtless cover all the outlines you should be okay. Study the homework and book (and obviously notes) to determine the exact knowledge you will be tested on.

Rida Ismail 2E

Oxidation number is added in Roman numerals in parentheses after the name of the transition metal. You only do this for elements that have more than one ox state.

Rida Ismail 2E

This can be determined through whether or not complete dissociation occurs in water. Strong acids and bases completely dissociate while weak acids partially dissociate.

Rida Ismail 2E

I believe he is referring cisplatin. I cannot tell you exactly what it does yet because I haven’t spent time studying it yet.

Rida Ismail 2E

It just means that it an lose and gain and e- depending on what it is reacting with.

Rida Ismail 2E

Scientific calculators will be allowed since he needs to retest us on the stuff from the final in addition to now.

Rida Ismail 2E

I don’t believe he will. I think the UAa and TAs host the review sessions

Rida Ismail 2E

BH2+ would be non polar because it is linear. BH2 itself would have a radical because B has 3 lone e- and H each has 1e-
Which would be a total of 5e-.

BH2- would be bend because it has 6e- so 4e- are bonding and there are 1 lone pair on B.

Rida Ismail 2E

Ok bonds relate to anything that has to do with double or triple bonds. If there is a double bond or triple bond there is a pi bond

Rida Ismail 2E

Yes I believe those are the most common.

Rida Ismail 2E

it depends on the atoms but in the case of C2H2Cl2 that can be cis or trans. Cis means that the Cl and H are on the same sides. This would be polar because there is a heavy pull on one side and not such a strong pull on the other side. in the trans molecule the Cl and H are distributed opposite from...

Rida Ismail 2E

They form the dsp^3 and the d^2sp^3

Rida Ismail 2E

Are u talking about the quantum numbers? Because no i do not believe those are.

Rida Ismail 2E

If you think about two electrons as magnets it makes a lot of sense. If teo amgnets are close together they will repel strongly but if you separate them then you can barely feel the force between thrm. In the same sense, the electrons will repel when they are close by but not repel as much when they...

Rida Ismail 2E

I think you have to draw to figure out what shape it would be, but i don't think we are being graded on the shape we draw judging by the fact that he told us we don't need to know how to draw the 3D shape.

Rida Ismail 2E

Going off of the last post, the bond order can change for resonance because all the bonds become the same because of delocalized electrons. So it is possible to have a 1.5 bond (1single and one double combining) or 1.33 bond (2 singles and one double combining).

Rida Ismail 2E

I believe that it would be nonpolar because u would only look at the atoms attached to the central atom and those are all O.

Rida Ismail 2E

I would say memorize all the basic ones. There are a few that he told us we don't need to know due to the fact that it varies per molecule (i believe they were the ones with lone pairs). So i would memorize all of the ones without lone pair and have a good understanding of how to predict the ones wi...

Rida Ismail 2E

It is different because the different atoms and lone pairs cause a varying bond angles. The repulsion seen in sulfite vs ammonia is different because of the ways in which each individual lone pair interacts with the other atoms.

Rida Ismail 2E

In a molecule the shape of it may allow it to fit into an activation site of an enzyme. But more importantly the H bond makes an enzyme or protein into the shape it is through secondary stuctures. If those h bonds are broken the shape is lost and the protein cannot preform its function.

Rida Ismail 2E

There do not always have to be dipole moments. Like in the Molecule H2 there are no dipoles because theoretically the electrons are perfectly shared because the electronegaticities are exactly the same. If there are dipole moments then they would cancel out if they are pulling equally in opposite di...

Rida Ismail 2E

Yes, I believe you would. And it would probably pertain to the new info that isn't on the midterm. Unless you're TA decides to do review problems for the midterm.

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