CHEMISTRY COMMUNITY

Andrea_Torres

What is the difference between the two? Does it affect which is anode or cathode and how if so?

Andrea_Torres

Yes I believe it should be the same where to get a C- you need 50% to pass.

Andrea_Torres

Since the final will be on ccle does that mean that we just input an answer or does work actually have to be shown? Cause without work there is no chance to get at least partial credit.

Andrea_Torres

Is the final up already? If so where would I find it? Is it due by a certain day?

Andrea_Torres

Since classes are cancelled does that mean that review sessions are cancelled as well? Will those also be online?

Andrea_Torres

How do we determine whether k is < or > 1? Also, why is it important?

Andrea_Torres

In the test, I remember that they asked to balance the reaction but how do I do that?

Andrea_Torres

In the Nernst Equation there is Q and I know that you divide one on top of the other but how do I know which is on top of the other?

Andrea_Torres

How do we know which one is being oxidized or reduced if they both look like they both received the same amount of electrons in half reactions?

Andrea_Torres

Are we supposed to know how to determine the value of the anode and the cathode? If so how do we do that?

Andrea_Torres

How do we derive the van't hoff equation when they say K1 and K2 exists?

Andrea_Torres

What is the purpose of the salt bridge in the cell diagrams?

Andrea_Torres

I know that n is the electrons but is it the one that is shown on the reactions when it says for example 2e-? Would the n be 2 in that case?

Andrea_Torres

What is a good technique for remembering this equation and what each variable stands for?

Andrea_Torres

Are we given when a reaction is anode or cathode or are we supposed to be able to determine that by ourselves? If so, how do we determine which is which?

Andrea_Torres

How do we determine whether work has been done on a system?

Andrea_Torres

What outline will test 2 be covering? Is it up to what we learned Friday or will in continue to week 8?

Andrea_Torres

That I know of Lavelle does not give any extra credit opportunities. Its mostly just all the points that you find out of the syllabus to reach the 500 points.

Andrea_Torres

A half reaction is either the oxidation or reduction reaction that makes up a redox reaction.

Andrea_Torres

Its 5 posts per week and the week ends on Sunday but at the end of the quarter you should have 50 posts total.

Andrea_Torres

How do we determine when there has been a phase change?

Andrea_Torres

How do we approach a problem when we are asked to look for the irreversible and reversible expansion? Is there different equations used for both expansions?

Andrea_Torres

What is irreversible and reversible expansion? How do we know which is which when faced with a problem?

Andrea_Torres

Something I have been struggling with is determining with work equation to use so how do I determine which work equation to use?

Andrea_Torres

It was said that it is easier to separate a redox reaction into half reactions but what does half reactions mean? Are reactions just cut in half?

Andrea_Torres

Since an isolated system has no exchanges with its surroundings, this means that the isolated system can not have a change in energy.

Andrea_Torres

I read on chemistry community that the x is ignored if the K Is less than 10^-3 but is K always going to be given? If not how will I know when the x should be ignored?

Andrea_Torres

A closed system is when energy can exchange with its surroundings, but an isolated system is when nothing exchanges with its surroundings.

Andrea_Torres

I know that in PV=nRT there is a gas constant but how do you determine which one is suitable for the problem?

Andrea_Torres

Is it possible that it can be given in a problem two different molarities? Does it matter when doing ice tables?

Andrea_Torres

How do phase changes affect a reaction? How do they matter?

Andrea_Torres

How do we do partial pressure? What is the difference between partial pressure and regular pressure?

Andrea_Torres

How do we use the quadratic equation? Which values go into each variable?

Andrea_Torres

What does each letter stand for?

Andrea_Torres

How do we know which way the equilibrium will shift?

Andrea_Torres

What does it mean for something to be additive?

Andrea_Torres

How do we add reactions to obtain net reaction? For example during lecture two of the reactions were N2 and 2NO equal N2 so how does that work?

Andrea_Torres

How are we supposed to make the chemical equation on our own when solving for concentration and down ice tables?

Andrea_Torres

Do they have specific values? I was doing problems 6D.15 and 6D.17 and they both have the same values.

Andrea_Torres

How do we find the value of x when it is not given?

Andrea_Torres

Why does temperature (endothermic & exothermic) matter? How do we know from solving a problem if it is endothermic of exothermic?

Andrea_Torres

In my discussion, when solving for x after doing the ice table we got x^2/(.10-x). Then when we plugged in the Ka= 1.8 x 10^-5 so the equation was 1.80 x 10^-5 = x^2/.10. Why is it that the -x was ignored?

Andrea_Torres

Why is it that H2O gets cancelled out when doing ice tables?

Andrea_Torres

Is there a reason we use H3O+ or is it just something we have to use for acids?

Andrea_Torres

In problem 6A.19 part c in the textbook it says its 3.1 mol/L however in the solutions manual it gives the value 3.1 x 10^-3. Is there a reason for that or is it just a solutions manual error?

Andrea_Torres

What is the difference between using Kc and Kp?

Andrea_Torres

The R in PV=nRT stands for the gas constant and its units are 8.314 J/mol·K.

Andrea_Torres

I see that there is the equation P= (n/v)RT which is connected to PV=nRT but why is it that V (volume) is not divided by the whole nRT? Since its only dividing by n (number of moles).

Andrea_Torres

Is reaction Quotient (Q) the same thing as K? If so then how is my answer not the same as what I would get for K? How do you solve if you don't have any values?

Andrea_Torres

When solving for K to the coefficients have to be in a particular order?

Andrea_Torres

When solving for K when you don't have any values is there a reason why we use P?

Andrea_Torres

In number 34 in the packet to get the molOH we multiplied the Mol of CaO times 2 mol OH why was it 2 mol of OH but H+ was only one?

Andrea_Torres

In C5H5NO2 it mention that one of the carbons has a hybridization of 2sp^2. What does the 2 mean? Can we just put sp^2 or does it have to be 2sp^2?

Andrea_Torres

Can someone explain to me how KA works and how this helps us find the pH?

Andrea_Torres

Can anyone recommend me some strategies for memorizing the names of the ligands?

Andrea_Torres

How can you identify which pair of atoms are most tightly bound?

Andrea_Torres

How do you know when the molecule given is an acid or a base? Or does it always have to be given?

Andrea_Torres

What is the difference between Lewis acids and bases and Bronsted acid and bases?

Andrea_Torres

It is most important to know that neutralization is a reaction between acid and base that ends with salt and water.

Andrea_Torres

It was discussed that a strong bases is completely ionized in water and weak bases are no completely ionized in wate. How do we know which one is completely ionized and which is not?

Andrea_Torres

How do we calculate the pH of acids and base? I know there is log involved but I don't get how to use it.

Andrea_Torres

I somewhat understand some of the concepts but applying them is what I find difficult. What would you guys suggest I do to help me study for the final exam?

Andrea_Torres

Can someone please explain to me what are ligands?

Andrea_Torres

When drawing the sigma and pi bonds is it basically just circling the bonds and mentioning its hybridization?

Andrea_Torres

Does the AXE formula only give us the shape of the molecule? Does it serve any other purpose?

Andrea_Torres

I know that a double bond it is a sigma bond and a pi bond, but when drawing it on the actual molecule do you just draw a pi bond?

Andrea_Torres

How do we determine hybrid orbitals? Is it just by looking at the Lewis structure or is it by looking at the valence shells?

Andrea_Torres

How is the VSEPR model used in determining shape? Is it also used in finding the angles?

Andrea_Torres

How is the VSEPR model used in determining shape? Is it also used in finding the angles?

Andrea_Torres

Can someone please explain to me what are sigma and pi bonds?

Andrea_Torres

How does repulsion help influence the molecular shape?

Andrea_Torres

In Friday's lecture Professor Lavelle discussed the structure/shape of Xenon Tetrafluoride but he showed it in an octahedral shape. How do we know that its going to be in that shape?

Andrea_Torres

How are we supposed to predict the bond angles? Do we use the shape name or the VSEPR model?

Andrea_Torres

What are resonance structures?

Andrea_Torres

I know that the L in the equation means the # of electrons in a lone pair but what is a lone pair?

Andrea_Torres

What is the difference between covalent and ionic bonds?

Andrea_Torres

Does each single bond mean 2 electrons?

Andrea_Torres

How does formal charge show us which has the highest energy?

Andrea_Torres

How do you know when it is ionic vs covalent?

Andrea_Torres

Is there a way to find the bond lengths?

Andrea_Torres

How do you know when to double bond?

Andrea_Torres

Is there a specific way that we have to draw the structure?

Andrea_Torres

I know that when there is a cation you have to remove one electron and when its an anion you should add one. When do I know to do that if you have both a cation and an anion?

Andrea_Torres

Can someone explain to me what are the n levels that Dr. Lavelle is writing on the board in lectures?

Andrea_Torres

Can someone explain to me how electron configuration works and how to use s, p, d, and f?

Andrea_Torres

a) To find the wavelength you usethe equation wavelength=c/v, c is the speed of light (2.997 x 10^8 ms^-1).
b) To find the frequency you use the equation v= c/frequency which was given to you (421 nm).

Andrea_Torres

The unit for wavelength is in meters but sometimes for some problems nanometers is used.

Andrea_Torres

To calculate for the energy you use the equation E=hv, h being Planck's constant.

Andrea_Torres

I am having trouble with this question: In the spectrum of atomic hydrogen, several lines are generally classified together as belonging to a series (for example, Balmer Series or Lyman series) What is the common to the lines within a series that makes grouping them together logical? Can someone exp...

Andrea_Torres

In order to answer part b of this problem, you first have to convert the 5.00 mg of sodium then divide the grams of sodium by the molar mass of sodium. Once you do that then you have to multiply this number by Avogadro's number to convert it into moles. After this, you multiply this value by the num...

Andrea_Torres

To solve this problem you have to multiply Avogadro's number by the value you got in Part a of the answer and you should get your answer. You are using Avogadro's number because you are given that it is only one mol.

Andrea_Torres

In the textbook, it says that the Balmer Series consists of n1=2 and the Lyman series is n1=1. What does this mean? Are they like levels in the atomic spectra? What does this work for?

Andrea_Torres

To find the energy of the photon you use the equation E=hv meaning in this case you multiply the given frequency (8.7 x 10^-14 Hz) by Planck's constant (6.626 x 10^-34).

Andrea_Torres

In the homework it referred to formula unit. Is formula unit any different mathematically than a molecule or atom? Will it affect any of my calculations?

Andrea_Torres

When solving this problem: 1. Multiply the mass given for CO2 of 0.682g x 1mol CO2/44.01g CO2 to convert the grams to moles then multiply 1 mol C/1 mol CO2 to get the mol of C which is 0.0155 mol. Do the same process for all the other elements given (H2O and N2) 2. Convert the moles you just found i...

Andrea_Torres

This might be a very dumb question but this was mentioned in my discussion the other day and I don't quite understand what they mean by significant figures. What is it?

Andrea_Torres

The easiest way to convert kg to g is to multiply the mass value by 1000 to get your grams since 1 kilogram= 1000 grams.

Andrea_Torres

Hi everyone! I have a question regarding the actual and theoretical yield. I know that to find the percent yield we have to divide the actual yield over the theoretical yield x 100%. How do I find the actual yield and the theoretical yield?

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