CHEMISTRY COMMUNITY

Samantha Chung 4I

I just wanted to double check, is "free energy of activation" referring to delta G difference between the products and reactants? Also, the difference is that in the presence of an enzyme, the delta G remains the same, whilst the enzyme provides an alternative pathway for the reaction (whi...

Samantha Chung 4I

I remember being told that Cv and Cp are differnet for diatomic molecules? Can someone tell me what it is again?

Samantha Chung 4I

On my discussion notes, I have that in a galvanic cell, the anode is connected to the positive terminal of the battery, and the charge on the electrode is negative. However, in many online sources, the anode is negative? I am confused as to the difference, or does the "terminal" and "...

Samantha Chung 4I

during todays lecture, for the NO(g) example that was done to illustrate pre equilibrium constant, how did we obtain 2k1k2/k1' = k? Just to clarify, the k is the rate constant (not equilibrium constant)?

Samantha Chung 4I

Do electrodes take part of a reaction in a concentration cell? For the problem 6. 53(d) - will increasing the mass of chromium electrodes lead to a greater number of Cr3+ in the anode side, hence effecting the Ecell value? Or are we assuming the chromium electrodes do not take part in the reaction?

Samantha Chung 4I

For 6N. 3A self test 7th editon, how do we know what is the product/reactant in Q as the question does not specify if the 1.0M of solution is on the left or right? Im assuming the saturated solution is the product, but why exactly is that the case?

Samantha Chung 4I

In a concentration cell, we are assuming E standard = 0, however, is not this only to when the concentrations are equal? What happens if the concentrations are not equal, but not at 1.0 M? Woudl this then render the equation invalid?

Samantha Chung 4I

In the 7th edition, question 6N.1, I was wondering if we would be expected to know how to write a reaction for a solubility reaction such as AgCl -> Ag+ and Cl- ? How do we determine which one is oxidized/reduced? Also how do we know what reaction to look out for in the appendix?

Samantha Chung 4I

How do we know when to apply the Nerst equation, are there hints in the question that I should look out for?

Samantha Chung 4I

I do not quite grasp the concept of "k" how do we determine the units of k, does k even have units?

Samantha Chung 4I

in class, it was mentioned that the gibbs free energy is the maximum work done, but then the equation is delta G = we maximum, however, is not we referring to expansion work (from the chapters for the midterm)?

Samantha Chung 4I

Since the Van T hoff equation is not given in the formula booklet, would we have to memorize it?

Samantha Chung 4I

Just to clarify, but if a question asks: at what temperature X reaction will be spontaneous, and the answer based on inequalities is anything below temperature Y for instance, do I write that, or can I just write any number?

Samantha Chung 4I

In the textbook examples given, sometimes gibbs free energy is given in kJ/mol and sometimes it is just kJ, how do I know which one to write? (In both cases, the units cancel out to kJ).

Samantha Chung 4I

The textbook gives a different method for balancing equations in acidic and basic solutions. How do we know whether the reaction is occuring in an acidic or basic solution?\

Samantha Chung 4I

For the equatins delta G = delta H - T delta S and Delta G = G (sum of products) - G (sum of reactants), am I right on saying that both can be used to calculate delta G naught and delta G, depending on the situation and what values are given? How do we distinguish between delta G and delta G naught ...

Samantha Chung 4I

Today in class, was electrical -> chemical energy, the one with a positive/negative delta G, what about chemical energy - electrical energy, is that positive or negative delta G?

Samantha Chung 4I

How do we distinguish when to use delta G = delta H - delta S temperature and delta G = Delta G (product) - Delta G (reaction)?

Samantha Chung 4I

Why is platinum often selected as an electrode?

Samantha Chung 4I

What is the difference between delta G knot and delta G?

Samantha Chung 4I

In the textbook, the equation for delta S = C In (T2/T1), but in Dr. Lavelle's formula booklet, the equation is S = nC In (T2/T1). Im confused about what equation to use?

Samantha Chung 4I

Is there a specific set of conditions under which we can assume q and w equals to zero? Or does it depend on the problem?

Samantha Chung 4I

For ths question, how do I tell the number of possible orientations for degeneracy in both molecules? For a molecule like Ch3Cl that was given in class, I know that it is 4^N, but how do I tell the number of possible orientations for a trigonal bypyramidal structure?

Samantha Chung 4I

How exactly does the temperature of a system remain constant while heat is being supplied to it does this relate to the delta U = q + w equation? Whereby, as the system has heat supplied to it, it is doing work and energy is released as well, because delta U = 0?

Samantha Chung 4I

It was mentioned today in lecture that the temperature of an reversible reaction both inside and outside the system has to be constant, why is this the case?

Samantha Chung 4I

The equation introduced today in class, U total = 3/2 nRT , I was wondering if this only applies to reversible reactions? Or does it apply to both reversible and irreversible reactions?

Samantha Chung 4I

When Dr. Lavelle introduced the -nRT (In V2/V1) equation, I was wondering if we see a problem, how do we know to assume whether or not it is an ideal gas? Will the question tell us?

Samantha Chung 4I

Why is it that in a closed system, when you move the piston up, the W value is negative, but when you move the piston down, the W value is positive (what Dr. Lavelle mentioned in lecture today)?

Samantha Chung 4I

When we talk about surroundings in chemistry, is there a "boundary" to the surroundings?

Samantha Chung 4I

In the 7th editon textbook, question 4A.1,why is the mercury in a thermometer an isolated system? Should not it be a closed system because the mercury will move based on the temperature of the surroundings?

Samantha Chung 4I

What exactly is heat capacity, and why is it a state property?

Samantha Chung 4I

Why is it important that delta H is measured at a constant pressure?

Samantha Chung 4I

I think that you first do 10^-(14-13.25) to find the OH - concentration in the diluted solution. Then you multiply that by 500/50 as that is the factor the original solution of 5ml is diluted by. However, the concentration calculated will then be that of the 5ml. After that you take that value and y...

Samantha Chung 4I

It was mentioned in class that if K is greater than 10^3, the products are favored and if K is smaller than 10^-3, the reactants are favored. However, if we look at K = 2.0 for example, would this still mean that the reaction proceeds towards the products, but the production of products are not favo...

Samantha Chung 4I

Since we should avoid using the comparison of number of moles of gas to explain our logic, for instance in HW problem (7th edition 5J 5). How do we explain whether the following will lead to more products or reactants?

2O3g) -> 3O2(g)

Samantha Chung 4I

Dr. Lavelle mentioned sometime that we cannot use the word "shifted", can we apply this term when talking about Le Chatelier's principle - for instance, the position of equilibrium shifts to the right if we add more reactants?

Samantha Chung 4I

I have a followup question: is there a difference between pressure and partial pressure in the context of this question?

Samantha Chung 4I

It is because the Kc is very small, that the change in negligible. I think the example that Dr. Lavelle gave was if you have a million dollars and you take for instance, a dollar away, the value is still very close to one million, so you can approximate it to one millon. After you do that, it is no ...

Samantha Chung 4I

I think that it is important if we include the phases, because it tells us what to use, for instance gases will be Kp -> also, it helps you know what to be written in the equilibrium constant.

Samantha Chung 4I

When calculating the value of K does the number of significant figures we record follow the rules we learned in 14A, or are there any special rules?

Samantha Chung 4I

As I was completing the reading section, I noticed that there was a "reaction quotient" - what is the difference between this sand the K value?

Samantha Chung 4I

During class today, a pure substance is not used in Kc, when I watched the video modules, an example was given with a dilute solution. But if the liquid is a concentrated substance, will that change anything?

Samantha Chung 4I

I understand the chelates need to be polydentate ions, and that there needs to be "spaces" between each atom with lone pairs to form a ring. Besides that, how do we tell if a compound forms a chelate, and further, if the chelate is stable?

Samantha Chung 4I

I noticed that for aqua in the textbook, sometimes its writtten as H20 and sometimes it is written as OH2, does this matter when writing the formulas for the names?

Samantha Chung 4I

For HW problem 6A.23, I understand that Ba(OH)2 will dissociate to form Ba2+ and 2OH- . Yet, I do not understand where the H30+ comes from after that? If it comes from water, why does not the water go into the original Ba (OH)2 dissociation equation?

Samantha Chung 4I

For the final, will we expected to know the names of more "uncommon" acids/bases? Sometimes the books gives some acids and bases that are not commonly seen.

Samantha Chung 4I

On the final, if it asks us for instance to write an equation showing proton transfer, and we get something like C6H5NH3 +, will we be told whether it behaves as an acid or a base, because this can accept protons and also donate protons?

Samantha Chung 4I

In the textbook 6C.3 (7th edition), it says that the stronger electronegativity values makes stronger hydronge bonds between H20 and H -A bond. But I thought that hydrogen bonds only apply to H bonded to O,N, and F within the same molecule. Can I assume then that the H bonded to O, N, and F is a con...

Samantha Chung 4I

I understand what a coordination sphere is on a diagram, but how do I explain this in words?

Samantha Chung 4I

How does cisplatin function (in terms of chemistry) to stop DNA replication?

Samantha Chung 4I

if the "orbitals of an H atom are said to be degenerate", is it that for instance 1s and 2p have the same energy, or is it just for instance 2s and 2p that have the same energy? But energy for 1s and 2p are still different because they have different principal quantum numbers?

Samantha Chung 4I

On my notes I remember writing down in the schrodingers equation lecture that higher energy leads to bigger orbitals? How do I explain this using schrodinger's equation?

Samantha Chung 4I

For a trigonal bipyramidal general shape, we would place the lone pairs on the equatorial axis because it has least repulsion with the surrounding axial atoms, as there are two axial atoms. However, for the square planar shape, why then do we place the two lone pairs on the two opposite ends, would ...

Samantha Chung 4I

How does the repulsion between two atoms when they get very close relate to the Pauli Exclusion principle?

Samantha Chung 4I

When instantaneous dipole dipole moments are produced at a greater rate, can we correctly say that the London forces increase in strength?

Samantha Chung 4I

It says here in the textbook that cations are highly polarizable if they are small and highly charged. Does one factor matter more than the other?

Samantha Chung 4I

When we say that for example, the bond angle for a bent shaped molecule is less than 120 degrees, how much smaller is it exactly? Is there a way to determine? Or is it influenced by other factors as well?

Samantha Chung 4I

We mentioned in class that the repulsion of lone pair electrons is greaer than bonding electrons, but why is this true?

Samantha Chung 4I

Does the arrangement of the dash and wedge matter when drawing the shape/structure of a molecule?

Samantha Chung 4I

I think Dr. Lavelle mentioned in class about how ionic bonds have covalent character, can someone please re-explain this concept?

Thanks!

Samantha Chung 4I

Hello! So in my lecture notes I have written, u=d x abs. value of q, I got confused on as to why q has to be in absolute values?

Samantha Chung 4I

For ONF, we are supposed to draw the central element as the element with the least ionization energy. In this case this would be oxygen as N and O are exceptions in the periodic trend. However, in the lewis structure of ONF, the nitrogen is the one at the center?

Samantha Chung 4I

Is there a way that we can deduce bond length of a resonsance structure by knowing their other bond lengths? For example, in NO3, we know the bond length of N double bond O and N singe bond O?

Samantha Chung 4I

During lecture on Friday, Dr. Lavelle talked about the Delta Negative region? I was wondering what this is referring to?

Samantha Chung 4I

HIi! Can someone re-explain to me why the formal charge has to be zero? This is something that I keep forgetting. Thanks!

Samantha Chung 4I

I remember when writing electronic configuratons, there were two exceptions Chromium and copper, I think professor lavelle mentioned "why" these are exceptions in class. Can someone re-explain this to me?

Thanks!

Samantha Chung 4I

I think during lecture on Wednesday Professor Lavelle mentioned about the electron affinity, what is the trend of the electron affinity down the group and across the period in the Periodic Table?

Samantha Chung 4I

Can someone re-explain the concept of covalent radius to me?

Thanks!

Samantha Chung 4I

On my notes, I have written down "the schrodinger's equaton operates a change on schrodinger equation function ((x,y,z) ) which equals to energy (schrodingers equation): (x,y,z). However, what does the (x,y,z) represent? And what is the relationship between schrodinger's equation and energy?

Samantha Chung 4I

I was just wondering: Is the uncertainty in the momentum of an electron bound by the probability density function? (Since the probability density function represents the chances of finding an electron in that area)? Is there a way to "compute" that?

Samantha Chung 4I

Hello! So I think he said in class something about "2s orbital appearing larger than 1s orbital?" Can anyone repeat the context to me?
Thanks!

Samantha Chung 4I

I remember towards the end of class, he said something about how a certain calculated wavelenght was larger than 10^-10(angstrom), and since we can "measure" the angstrom, we can measure that as well. So I am guessing he was referring to the Angstrom.

Samantha Chung 4I

Electron transitions basically means that an electron goes from one energy level to another, in the process giving off energy as a photon of light. In high school I learned that as the n levels approahces infinity, the electron is infinitely far away from the nucleus, therefore experiencing weak for...

Samantha Chung 4I

Hello! Im just commenting because I had the same question, but Im not sure whether or not he said "can be seen" or can be measured as per laboratory measures? For instance one angstrom is 10^-10, so chemists can definitely "measure" that. He might have meant that anything smaller...

Samantha Chung 4I

I usually pick one atom to start with then deduce the rest accordingly. There was a problem we did today in discussion where we wrote one of the ratios as a fraction(I think it was 25/2). Then we multiplied the entire thing by two to get integer values. I think thats useful as well!

Samantha Chung 4I

Hii! Did anyone understand the part where he said n(energy levels) cannot be numbers such as 1.24 or non integer values etc. ? I didnt quite understand that part?

Thanks!

Samantha Chung 4I

Hii! For me, I calculate the reactant that is the limiting reactant first, then I use the number of moles of the limiting reactant to calculate that of the products. I think the reason for this is because the products produced cant be "greater"than that of the limiting reactants. (But corr...

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