CHEMISTRY COMMUNITY

Bijan Mehdizadeh 1B

Organic molecules and naming will not be on the final, right?

Bijan Mehdizadeh 1B

Is everything up until our last lecture on Friday going to be fair game for what's to be covered on the final?

Bijan Mehdizadeh 1B

Also, we don't have to know the organic molecule naming topics and what not that are starred, right?

Bijan Mehdizadeh 1B

Hi, I was wondering if there is a practice final circulating on chemistry community like Lyndon's midterm. If so, how would I find it?

Bijan Mehdizadeh 1B

Hi, I was just wondering what the stars to the left of some of the chem 14b topics, like naming compounds, mean. Thanks!

Bijan Mehdizadeh 1B

I don't know if you can balance that specific reaction because there is H on the product's side but not the reactant's. Maybe you have to assume there is another reactant involved kind of like the acid base reactions when H20 is not always shown as a reactant

Bijan Mehdizadeh 1B

Yes, you can do with any of the reactants as long as the other reactants are in large excess

Bijan Mehdizadeh 1B

Will the final be cumulative? And if so, will it contain any material from chem 14a or just all we have learned in 14b?

Bijan Mehdizadeh 1B

Why does H+ show up in both a and c cell diagrams, and why is H+ part of the cathode reaction in both?

Bijan Mehdizadeh 1B

How do you know that Fe 2+ becomes Fe 3+ and that MnO4- becomes Mn2+ in 6L #9?

Bijan Mehdizadeh 1B

Just to make sure, nothing in Monday's lecture will be on Test 2, right?

Bijan Mehdizadeh 1B

How would we be able to get a regrade for certain midterm questions?

Bijan Mehdizadeh 1B

Are all the equations we need to use going to be provided to us on Test 3?

Bijan Mehdizadeh 1B

For 6L5 c, how do you determine whether you make the half reaction h2 --> hcl or cl2 --> hcl? There is one product, but cl2 is reduced while h2 is oxidized, so I was wondering how come hcl is only used in the anode half rxn eq for h2

Bijan Mehdizadeh 1B

For 6L5 b, why do you have to add platinum to the redox reaction?

Bijan Mehdizadeh 1B

Why do some cell diagrams separate their reactant and product for a half reaction with a vertical line and some separate them with a comma?

Bijan Mehdizadeh 1B

I was wondering if the total reaction derived from the cathode/anode half rxns needs to have a specific order to it or not? I know the cell diagram is supposed to be anode on the left and cathode on the right. I am just unsure if there is a significance to the order of reactants and products in a re...

Bijan Mehdizadeh 1B

I remember one of my family members asking me this question, but I forgot the answer and am quite curious to what it may be. The question was, if you have a spring, and you compress it, and then put a rubber band over it to keep it compressed, and then you throw it into the fire, and it disintegrate...

Bijan Mehdizadeh 1B

I know we learned in lecture that delta G is equal to w-max, but has a real life process ever produced the results of delta G equaling w, meaning that all the free energy available was used to do useful work, or is this close to impossible to ever even happening?

Bijan Mehdizadeh 1B

Besides research in the field of thermodynamics, I believe there are also thermodynamic engineers as well as physicists that deal more specifically with either the theory or application of thermodynamics. I don't know about many life science applications since thermodynamics tends to focus on chemic...

Bijan Mehdizadeh 1B

Hi. I was wondering why the solution manual is using -417.5 kJ/mol as the enthalpy of formation for K2S when the appendix of the book says it's -471.5. Is this an error, or am I missing something?

Bijan Mehdizadeh 1B

I believe it is because we are assuming that the reaction is isothermal and reversible, which is theoretically supposed to yield the highest enthalpy and entropy, so we apply entropy and enthalpy as maximums for such reactions

Bijan Mehdizadeh 1B

It depends what values you are given and which one(s) you need to find. However, R is only used in reversible isothermal reactions while C is used when temperature is changing, and you use Cv or Cp depending on whether volume or pressure are constant.

Bijan Mehdizadeh 1B

At standard conditions, temperature is 25 degrees Celsius or 298 K, so I would see if the question specifies that it takes place under standard conditions, because then you can assume the temperature to be 298 K. Pressure would be 1 atm and n would be 1 mol at standard conditions as well, so I would...

Bijan Mehdizadeh 1B

Do we have to draw the Lewis structures every time we use bond enthalpies?

Bijan Mehdizadeh 1B

Hi. I was wondering how to solve 4A7 because I keep solving it and getting the wrong answer. I know you have to use q=mc(delta T), but I don't know how all the values factor into this equation.

Bijan Mehdizadeh 1B

Hi. I'm having a difficult time solving 4B #5 as I don't know what equations to use. Could someone please explain this? Are we even at this point in the lecture notes, or have we not gone over these concepts yet?

Bijan Mehdizadeh 1B

I was wondering how to solve 6D15 because I keep getting the wrong answer. I take the negative log of the concentration to get PH or take the negative log and subtract from 14 to get pOH. Am I supposed to make an ice table?

Bijan Mehdizadeh 1B

I was wondering if anyone knew how to solve this problem. I found the h+ and oh- concentrations for a and b respectively, but I don't know how to find the initial concentrations of the weak acid/base.

Bijan Mehdizadeh 1B

Could someone please explain how to solve 5I #23 please? I set up an ICE table and solved, but I didn't get the correct answer.

Bijan Mehdizadeh 1B

Hey, I was just wondering when the deadline is to post 3 times on chem community. I heard from some people that the deadline is sunday every week, but is that true?

Bijan Mehdizadeh 1B

Hey, just wanted to add that when doing the hw problems, the later numbers are typically the most helpful as they are usually the hardest and incorporate the most out of that section. Good luck!

Bijan Mehdizadeh 1B

When is our next homework assignment due? Are we turning it in in our next discussion section?

Bijan Mehdizadeh 1B

Cl2 cancels out when you take the two equations that make up the final equation into account

Bijan Mehdizadeh 1B

Why do we write K' when referring to K values that have fraction mole ratios? Is K' really the derivative of K in this case?

Bijan Mehdizadeh 1B

If we are asked to find K, do we assume it is Kc or Kp?

Bijan Mehdizadeh 1B

Hi. I was just wondering if it is ok to keep our same chemistry community ID even though our section is different this quarter. Thanks!

Bijan Mehdizadeh 1B

Hi. I was wondering, do we have to know both the old and new convention ligand names for writing the formula based off the name? Also, when writing the name of the compounds, would using either convention work or is one preferred over the other? Thanks

Bijan Mehdizadeh 1B

I know that we should know how to calculate pH using the concentration of H+ ions, but will we also be expected to find concentration from pH?

Bijan Mehdizadeh 1B

Could someone please explain what creates a dipole moment, and how to determine polarity from these dipole moments?

Bijan Mehdizadeh 1B

Could someone please explain to me how you know a compound is polydentate and if so, how to tell the number of places on the ligand that can bind?

Bijan Mehdizadeh 1B

Could someone please explain to me what en and edta are?

Bijan Mehdizadeh 1B

Does it matter the order of the molecules in the complex? Like for 7th edit 9C3d, would it matter if (OH2)2 came before or after (C2O4)2 when writing the coordinate complex formula?

Bijan Mehdizadeh 1B

Is it acceptable to write the water ligand as H2O instead of OH2?

Bijan Mehdizadeh 1B

Why would cobalt in this complex have a +3 charge? If NH3 has a -5 charge, and sulfate has a 2- charge, wouldn't that not balance the charges to +1?

Bijan Mehdizadeh 1B

Are there any certain examples of coordination compound biological applications that we will likely need to know for the final? If so, which would be the most emphasized?

Bijan Mehdizadeh 1B

I remember writing in my notes that van der waals reactions are interchangeable with London dispersion forces, but the book says that van der waals consist of dispersion forces, ion dipole rxns, and dipole dipole rxns collectively. I'm a bit confused as to the definition of van der waals reactions, ...

Bijan Mehdizadeh 1B

Interesting. Who knows if other units will become defined by formulas!

Bijan Mehdizadeh 1B

Hybridization has to do with the number of bonds only while the shape of the molecule takes lone pairs into account along with the number of bonds. For example, a trigonal planar and trigonal pyramidal molecule both have a sp2 hybridization even though they are different shapes. They both have three...

Bijan Mehdizadeh 1B

Hi. I was wondering why the reduced anion C6H4O2 2- is shown the way it is in the back of the book because I counted 34 valence electrons from adding 2 electrons to the model they have below the question, but the valence electrons I counted even for the formula differ from how many electrons are in ...

Bijan Mehdizadeh 1B

Have we learned about VSEPR formulas yet? If we have, how would you find them, like in 7th edit 2E13?

Bijan Mehdizadeh 1B

Is there a way to calculate bond angles, or do you just have to estimate them with a range? And if you can only estimate, how would you know that the bond angle for clo2+ in 7th edit 2E 5 is slightly less than 120 degrees?

Bijan Mehdizadeh 1B

For questions in 7th edition like 2D1 and 2D7, are we supposed to just look at electronegativity values? If so, where are they in the textbook?

Bijan Mehdizadeh 1B

Hi, I know this is a bit of an odd question, but I was always curious whether or not chemical structures can be expressed in 4-D. For example, trigonal planar can be expressed as a 2-D model, and trigonal pyramidal can be expressed as a 3-D model. I know the concept of the 4th dimension is still up ...

Bijan Mehdizadeh 1B

I know this topic has already been discussed thoroughly, but I always thought of hydrogen bonds as the "stronger of the weaker bonds" and the "weaker of the stronger bonds". The accuracy of this statement may be questionable, but it is a way I have always thought of hydrogen bond...

Bijan Mehdizadeh 1B

Like Brian said, any element in period 3 and beyond can have an expanded octet. If it makes it easier, I think of it this way: the element in period 2 that has the most amount of ground state electrons is Ne. Ne had 10 e-, but with those 10, it is stable, whereas fluorine has 9 e- and is likely to w...

Bijan Mehdizadeh 1B

For number 5, I keep getting .127 M after setting the problem up like (.211 M)(.150 L) = M2(.250 L). But in my notes, I believe Lyndon got 1.69 x 10^-2. I was wondering if anyone knows what I am doing wrong. Thanks!

Bijan Mehdizadeh 1B

Thank you so much for your time and help, Lyndon!

Bijan Mehdizadeh 1B

I have realized that a good amount of my posts have been about the technicalities regarding the homework and tests and not necessarily just about the chemistry content. Would those questions that are not in the unit categories still count as posts? Also, I remember Dr. Lavelle saying how comments ab...

Bijan Mehdizadeh 1B

If we did not post 3 times on chem community one week, can we post extra the next week to make up for that previous week?

Bijan Mehdizadeh 1B

Why is it that P^3- still has a larger ionic radius than S^2- and S^2- has a larger ionic radius than Cl- if they all have the same number of electrons?

Bijan Mehdizadeh 1B

I also heard that the test is going to be more conceptual, so I think as long as you know how the equations relate to each other as well as what the variable/parameters represent, you should be fine for the most part.

Bijan Mehdizadeh 1B

Interesting. I remember I posted last Sunday for this week, so could that still count for this week?

Bijan Mehdizadeh 1B

Interesting. I remember I posted last Sunday for this week, so could that still count for this week?

Bijan Mehdizadeh 1B

I believe the threshold energy is also the work function kind of like how a wave function is essentially the same as an orbital

Bijan Mehdizadeh 1B

Hi, I didn't know where to post this question, but I was just wondering when the deadline is for posting on chem community per week because some people I think said Friday but today is Saturday, so would this post still count for this week or next week?

Bijan Mehdizadeh 1B

Hello everyone. I was wondering if our second test will be this week (the discussion of week three) or next week (the discussion of week four). Thanks

Bijan Mehdizadeh 1B

We don't need a blue book for test 1, right?

Bijan Mehdizadeh 1B

Hello. I have been having some trouble with problem M1 in the 7th edition. I keep using the actual yield as 25.2 g and the theoretical yield as 36.0 g as I got that form the 35.0 g ammonia provided in the question, but when I calculate percent yield, I keep getting 70.0 % when the answer is actually...

Bijan Mehdizadeh 1B

I was also wondering about this question. What would you do with the grams given for the molecules like h20 and co2? I am used to the problem giving the mass of just the individual elements. I tried to solve for the individual masses by saying there are 2 mol of o in 1 mol co2 and 1 mol of c in 1 mo...

Bijan Mehdizadeh 1B

I was actually wondering the same thing recently as the concept of the mole was one that always baffled me. 2H corresponds to 2 moles of hydrogen atoms while H2 refers to a molecule consisting of two hydrogen atoms bonded together, thus forming a completely different compound. Therefore, the 2 in 2H...

Bijan Mehdizadeh 1B

Hello. I was wondering if the 4 modules for the chem review are due this Friday along with the 7 problems, or if they are due on a different day. Also, I saw that we can retake them, so does it take our highest grade or just the grade after our first attempt or is it just an effort grade?

Bijan Mehdizadeh 1B

Hello, I was just wondering if the 7 problems for homework are supposed to be written in pencil or pen or if it doesn't matter. Thank you!

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