CHEMISTRY COMMUNITY

diangelosoriano

To determine the sign, think about if the work is done to the system or by the system. W is positive if work is done by the system, and negative if work is done on the system

diangelosoriano

I'm pretty sure we don't have to know about lattice enthalpy for the final, and if there aren't any homework questions about it, it's safe to assume it will not be covered.

diangelosoriano

Under the class website, there is a section with the lecture outlines with all of the concepts we need to know. The outlines include which equations we need to understand how to derive

diangelosoriano

When a process is adiabatic, there is no transfer of heat or matter with surroundings, so all of the energy is transferred to surroundings as work. In this process, deltaU equals w.

diangelosoriano

When you reverse the direction of a half reaction, you also change the sign of the reaction potential.

diangelosoriano

Yes, the anode is always on the left of the salt bridge / porous disc, and the cathode on the right.

diangelosoriano

The electrons in each half-reaction have to be equal before you can create the overall balanced reaction.

diangelosoriano

There are no catalysts in this reaction.

diangelosoriano

Will we be expected to make distinctions within functional groups on the test? For example, being able to identify what type of amine group?

diangelosoriano

How do we know when to use a steady-state approximation or assume pre-equilibrium condition when we calculate the overall rate law from a mechanism?

diangelosoriano

Also, if you look at a reaction profile, you can see which is the slow step / fast step based on how high the energy barrier is. A smaller barrier would indicate fast step, and a larger one, slow step.

diangelosoriano

I am confused as to where we would need to apply this. What type of problem would involve this concept?

diangelosoriano

The course outlines show that we must be able to balance both; check the outlines posted on the class website to see all the material / concepts we need to know for each section.

diangelosoriano

Like previous exams, we will be given the reaction potentials needed to solve the problem; we are not expected to memorize them.

diangelosoriano

Will we also be expected to remember examples of molecules with functional groups?

diangelosoriano

The line structure can be turned into the full structure and vise versa, they are just different ways to represent the molecule.

diangelosoriano

Are there other examples of things that are generally homogeneous catalysts that we should be aware of?

diangelosoriano

The energy barrier will be steeper corresponding to a slow step, a smaller barrier would correspond to a fast step.

diangelosoriano

If a catalyst were added, how would this also affect k or activation energy?

diangelosoriano

Is there a way to tell by looking at these equations if the catalyst was heterogeneous or homogeneous?

diangelosoriano

How do we compare these terms to graphs / visually?

diangelosoriano

Are there ever occurrences of negative orders less than -1? Will these be possible / conceptually what would that mean in relation to rates / changing concentration?

diangelosoriano

Tiffany Dao 1A wrote:you can find [A] at 115 seconds by converting the [B].
[A] = 0.153 molA/L - [0.034 molB/L x (2 molA/1 molB)]
then you can use ln[A] = -kt + ln{A]o

Why do we subtract [0.034 molB/L x (2 molA/1 molB)]? Is there an equation on the formula sheet that we derive this from?

diangelosoriano

Determine the rate constant for each of the following first-order reactions:

Part C) 2A-->B+C,given that[A]0 =0.153molxL^-1 and that after 115 s the concentration of B rises to 0.034 molxL^-1.

I am confused as to where to start with this problem?

diangelosoriano

Is there a way to determine if the order of a reaction is 1/2, 1/4, negative, etc. just by looking at data from trials? Will we need to be able to determine these types of orders for any tests?

diangelosoriano

Since the pH is just a measure of the concentration of H ion concentration, we can use the Nernst equation to find it.

diangelosoriano

You must also be sure to make the distinction between capital K and lowercase k when we deal with kinetics (rate constant).

diangelosoriano

Please post the question? It would help other people also compare answers

diangelosoriano

For problems where you need to equate q to negative q (dropping a copper cube into water), does it matter if the negative sign goes on the system side or surrounding side?

diangelosoriano

The addition of the inert gas in itself will not affect the concentration, but since the inert gas is taking up space in the container, it is adding to the pressure of the whole system. When pressure is increased, the reaction will shift to favor the side with less total moles of gas.

diangelosoriano

Since the shape of a molecule is altered by lone pairs (i.e. water), the lone pairs will affect the dipole moment in that it "pushes" around the other atoms.

diangelosoriano

You should also be sure to be aware of the exceptions to the periodic trend rules. (Ex: noble gases not being included in the general electron affinity general trend)

diangelosoriano

Delocalized electrons are not associated with a single atom or covalent bond, so yes, a resonance structure would include the movements of delocalized electrons.

diangelosoriano

Strong bases include group one and two hydroxides and oxide like KOH, NaOH, etc.

diangelosoriano

Another method is to determine the stability of the conjugate base. If it is a very stable structure, the acid is strong. If the resulting conjugate base has an unstable structure, the acid was weak.

diangelosoriano

A method you can use to determine the strength of an acid is to look at it's conjugate base. Drawing the the Lewis structure of the conjugate bases will help you to determine stability.

diangelosoriano

Is there a certain time when an acid or base reaction should be considered a Arrhenius, Lewis, or Bronsted Acid / Base? How do you know when to use each type / definition?

diangelosoriano

Perhaps you are expected to balance before solving

diangelosoriano

Should we memorize all of the exceptions for the final?

diangelosoriano

Is there a time to use the 5% approximation versus using the value of K to determine if x is negligible?

diangelosoriano

In a review session, an example was brought up of an acid that had a PH of 10. How is it possible for an "acid" to have a PH that is considered basic (above 7)?

diangelosoriano

Is it possible to use an ICE chart if there are more than 2 reactants / products?

diangelosoriano

Will we be expected to be able to calculate at different temperatures for the final?

diangelosoriano

Can anyone explain how pi and sigma bonds change with resonance structures?

diangelosoriano

Here is another thread on the forum addressing the same topic, it may be worth the read:
viewtopic.php?t=8812

diangelosoriano

Does anyone know if we are expected to have the whole chart memorized for the final?

diangelosoriano

Chlorophyll is also another biological example, with a very similar structure to that of hemoglobin.

diangelosoriano

I'm also curious as to what the equation can be applied to in real life situations. Can anyone elaborate on that?

diangelosoriano

I'm pretty sure if you have a discussion that is before your lecture, you should complete homework that is up to date with that. Otherwise, do homework corresponding to how far he got in your lecture

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