CHEMISTRY COMMUNITY

nathansalce 3e

What are the two methods of finding the Reaction Mechanisms, how can you tell them apart, and will we be applying both on the final? I faintly remember Professor mentioning something about excluding one method, or perhaps i misheard. However, can somebody clarify for me?

nathansalce 3e

In the example Professor was showing today, are you essentially solving for the slow step? You dont determine from the beginning which one is which step, you just see the potential to substitute an intermediate to create the slow step out of one of the steps? Is it something like that? Because the s...

nathansalce 3e

Is there any good way to memorize the orientations of each organic molecule rather than just pure memorization? Any handy tricks, tips, mnemonics etc?

nathansalce 3e

No it does not imply constant pressure. Expansion against an external pressure however, I think implies an irreversible process. The word that might imply constant pressure would be constant itself.

nathansalce 3e

I think since the derivation of the equation speaks in general terms and has no specific definite value to integrate for, much like all the derivations we have done. I think all of our derivations thus far have been indefinite integrals meaning we are just integrating the variables, which is the imp...

nathansalce 3e

When solving first order reactions, when is it best to use the default ln in the equation, and when is it best to convert ln into log using its 2.303 conversion?

nathansalce 3e

The general example of a third order reaction is one where 3 molecules must collide, making it unlikely to occur as this is an unlikely event.

nathansalce 3e

I just wanted to clarify the graphs associated with first order reactions. Since there is an ln in the graph, is there a curve to the graphs? Or is it still linear. Or are there two graphs one with exponential one without?

nathansalce 3e

What is the general significance between a zero, first, and second order reaction. What is the conceptual difference beyond the fact that the slopes of change in [R ] is different. Of what importance does classifying reactions serve?

nathansalce 3e

So in the context of equilibrium from 14A and the context of this chapter how does the values of K and Q in reference to their value against 1 (If K is greater than 1, then x. If K is less than 1, then y). Are the concepts the same no matter the contexts? Or do they change depending on which chapter...

nathansalce 3e

since R T and F are all constants in standard conditions, these three constants can be multiplied and calculated to be 0.05916, just to simplify the process of calculations.

nathansalce 3e

Test 2 is this week and we finished electrochemistry during the midterm. Is there anything the test plans on focusing on? Are there concepts I can omit, Did Professor say anything about what may or may not be on the test for this week?

nathansalce 3e

Will there be Derivations on Midterm 18W? Which derivations will we need to know? Or do we just have to apply concepts of connecting two derivations?

nathansalce 3e

What are the conceptual differences between the 2nd and 3rd laws of Thermodynamics?

nathansalce 3e

There is no lecture Wednesday, the 14th for Chem 14B, just announced today.

nathansalce 3e

To create a redox reaction, one of the methods is to take both standard reductions of the compounds of interest, make sure the equation is balanced, and then flip the sign of the second reduction. This flipping of the sign of the standard reduction, is that the same thing as converting this reductio...

nathansalce 3e

Yes, the solvent of these solutions is typically water while the solute is the metal ions being transferred back and forth via the discharge of the battery.

nathansalce 3e

Gibbs free energy is calculated as a maximum. in an ideal state, in constant pressure and temperature, we would not lose some of this energy to "useless" actions. It's similar in concept to a chemical reaction... the Maximum yield is the maximum under perfect conditions and no error.

nathansalce 3e

There is no significant difference. deltaG_r is used in specific practice , while deltaG is an overarching, more general term

nathansalce 3e

The anodes permanent state is negative as it has extra electrons to give off (zn2+) , thus the electrons are always leaving the left side, or the anode. The charge is always negative and the negative charge is always leaving to the right side, the cathode. The anode loses some of its negative charge...

nathansalce 3e

Reversible expansion represents the maximum amount of work that can be done in perfect conditions where pressure is constant. Thus, the graph showing the maximum amount of work would be the reversible expansion graph, which correlates to the ln graph, the ln creating the slowly decreasing slope unti...

nathansalce 3e

Technically, we do not assume that deltaH and deltaS are constants... but rather we assume the difference in deltaH and deltaS between the two equations (for the two temperatures) is the same.Thus, we say that the rate at which H and S change is not the same, but the difference between the two value...

nathansalce 3e

More specifically, what is their conceptual importance for this chapter? When are they significant and how should I be able to recognize the big differences in between them?

nathansalce 3e

To add onto this, in any system DeltaU=q(heat)+w(work) . In a closed system, more specifically, only energy can be transferred, so therefore DeltaU in a closed system =q.... just the energy transfer that takes place in between the system and its surroundings. In an isolated system, energy nor matter...

nathansalce 3e

^ Not quite. The change in entropy is a state property, so to calculate entropy would not depend on the path taken to change the entropy. Therefore, it is not a difference of reversible vs irreversible reaction. R is the gas constant and C is the heat capacity so I believe the difference lies in the...

nathansalce 3e

It is only isolated systems where neither matter nor energy can be transferred in or out of the system. In a closed system, energy is freely transferred throughout the system, but not matter. Heating or cooling by altering the surrounding temperature will have an effect in energy of the system

nathansalce 3e

Does anybody know, in terms of the assigned homework for this chapter, what numbered problems correlate to what we are actually being tested on in Week 3?, Professor has talked about omitting part of the chapter, the part he is teaching next week, but what numbered problems should I be doing to prep...

nathansalce 3e

Can somebody explain the significance of PV=nRT and the role it plays in the chapter. How does it relate to enthalpies? Does it have some relationship to DeltaU=q+w, and can you explain it?

nathansalce 3e

Can somebody explain the difference between heat capacity and specific heat capacity and the significance that they both hold on this chapter. When is one important and when might you consider one or the other?

nathansalce 3e

The difference between reaction enthalpy and enthalpy of formation relies on the info given. Reaction enthalpy would require the use of Hess's Law, but in order to execute Hess's Law, you must know/ be given the total change in enthalpy a specific reaction produces. Typically this is given to you in...

nathansalce 3e

in addition, I believe there is another notation of enthalpy, such as q_v, or the enthalpy at a constant volume.

nathansalce 3e

in 93A, the conditions are listed, "1 bar, and 25* Celsius" Water is liquid at room temperature. Typically most of our problems will have to do with reactions occurring at 25*C, or the standard state of a substance, so this is what you should consider most of the time, especially in doubt.

nathansalce 3e

The H at the end is actually really easy to get rid of. Im not entirely sure if this makes the molecule a strong acid, but nevertheless: The COO chain is really good as acting as an electron withdrawing body, as to stabilize that last O.... What this means is that COO spreads the negative charge (Ca...

nathansalce 3e

Yes i agree with above, both [H 3 O + ] and [A - ] start out with having a zero concentration. But after dissociation of the reactant in water, both [H 3 O + ] and [A - ] increase by x amount, as seen in a drawn ice table. If they both increase by x, you can equate them since their values are equal,...

nathansalce 3e

If a molecule is either a Bronsted base or Bronsted Acid, does it have a corresponding Lewis Acid/Base characteristic? Or are both Lewis and Bronsted classifications exclusive from one another? Also what is the purpose of deciding whether or not a molecule is a Bronsted Base or Acid? For example, It...

nathansalce 3e

I really like this concept ^. But if that somehow doesn't help, it might help to think of it this way. Endothermic means for a reaction to require heat, which means that if heat is increased, more reactants will be able to turn into products. However, Professor says for the opposite is true. If the ...

nathansalce 3e

Nh₃, or ammonia, is definitely polar. Nitrogen is more electronegative than hydrogen, thus pointing the dipole moments to the nitrogen. Nitrogen's lone pair pushes the hydrogen away, thus making the dipole moments point in a common direction without cancelling out, making Nh₃ a polar molecule.

nathansalce 3e

So it doesn't quite matter whether or not, you put OH 2 or h 2 0, the only difference is that the former implies that Oxygen is the bonding atom on the coordinate compound. They both should be correct, however Dr. Lavelle insists on good practice so that we highlight the things appropriate and useful.

nathansalce 3e

I understand that Partial Pressure can be measured in two different fashions, atmospheres and pascals. When do we know to use each one and which is better in certain situations?

nathansalce 3e

Can somebody explain to me the basic definition of a Ligand? I understand the concept around a Ligand but i feel like i have a weak foundation for any of this knowledge. What is a ligand exactly and what are its functions/ implications / etc?

nathansalce 3e

Lavelle was also discussing the importance of Chelates in real life. Chelate's purpose is to bind onto metal atoms with a typical (II) or (III) oxidation state. This is has a positive functional use to remove metal ions from a solution per se. This can also be used to remove metal poisoning inside a...

nathansalce 3e

Can anybody expand on how dipole moments are first determined (like what direction do they go in and how that's understood) and then describe to me how the combination of dipole moments creates polarity?

nathansalce 3e

As far as I understand, the octet rule only applies to energy levels n=1, n=2. Any element in the n=3 energy or above may have an expanded octet and bond more than 4 times or have a combination of more than 8 electrons.

nathansalce 3e

I understand that if you were to combine resonance structures into one diagram, you would use dotted lines to depict the possible places of the bonds that are in resonance. How might you show resonance structure concerning lone pair electrons?

nathansalce 3e

Can anybody explain to me the basics of what a wave function is and what its importance in the chapter. I feel as it is an important concept that I do not understand and it makes the rest of my knowledge unsteady. What is its purpose and what do we need to know about it?

nathansalce 3e

The answer would be C)The more precisely the position is determined, the less precisely the momentum is known in this instant, and vice versa. Heisenberg's uncertainty equation involves the concept that the more we know about either position or momentum, the less we know about the other. The way we ...

nathansalce 3e

So if an object has a wavelength of less than x10^-15, its wavelength is technically undetectable or just so small that is irrelevant has little to no functionality. However, does it technically have a wavelength still? Do we consider it as an object that still has a wavelength? or if its value is s...

nathansalce 3e

When an electron drops down to a lower level, the atom loses energy in the form of electromagnetic radiation. When an electron jumps up a level, the atom gains energy instead. Whether its positive or negative can depend on the question being asked. "What is the change in energy of the atom?&quo...

nathansalce 3e

Can somebody explain to me why Planck's constant is measured in Joule Seconds. What is the significance of this unit and how does it relate to the equations its involved in? I originally thought Planck's was in joules per second, but was mistaken when i later discovered the truth. I am trying to fin...

nathansalce 3e

Can somebody better explain how a photon is both a particle and a wave? I understand that it acts like both, but in what situations does it act like wave and vice versa?

nathansalce 3e

And adding onto the above post, I believe the latter is doing nearly 2x as much work, so learning the stoichiometric ratio method would probably be much more efficient as you can identify which is in excess pretty quickly with some stoichiometry and some comparison. I have not run into a problem tha...

nathansalce 3e

On the test on 10/6/17, I had trouble allotting enough time to answer all the questions and I believe it was mostly as a result of me taking my time thinking about what significant figures I should be using throughout my intermittent calculations. Are significant figures a crucial part to the test o...

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