CHEMISTRY COMMUNITY

Alexia Joseph 2B

In addition to what was said above, I remember based off each functional group. Here is a list of the ones we learned in class. When there is an OH (hydroxyl group) : - Alcohol (there is an OH group at the end of a carbon chain), ex. C-OH For an O single bonded to 2 carbon s: - Ether (O is in the mi...

Alexia Joseph 2B

Given the instantaneous rate of reaction is 1.43 * 10^-2, and the initial mass of each reactant is 0.6 confined to a 750 mL vessel, how do you find the rate constant?

The rate law is rate = k [NO]^2 [O2]

Alexia Joseph 2B

Are you supposed to just determine it based on the rate equation, so that doubling oxygen makes the rate 1/2 slower, or halving the amount of NO makes the rate 1/4?

Alexia Joseph 2B

The problem is: Given: 2NO + O2 = 2NO2 The rate of the reaction was first order wrt O2, and the rate was second order wrt nitrogen monoxide. How are you supposed to find the effect of changing the amount of oxygen/amount of nitrogen monoxide? More specifically, How do you find out what happens to th...

Alexia Joseph 2B

Hi,

This question asks to calculate the entropy change for a monoatomic ideal gas at 1 atm, 303 K, and in a balloon of 53.48 L when the gas is heated to 333 K at a constant volume.

When calculating the n=PV/RT, why do you use the initial temperature instead of the final temperature?

Alexia Joseph 2B

I'm still kind of confused going, how can you tell if something is expanding irreversibly vs. reversibly?

Alexia Joseph 2B

I'm still kind of confused. How do the rate constants at different temperatures relate to the Arrhenius equation, and how do you solve these problem types where you need to determine either a rate constant or the activation energy. Basically, how do you set up with Arrhenius equation with rate const...

Alexia Joseph 2B

Why is it important to study the SN2 reaction in the chemical kinetics section?

Alexia Joseph 2B

When using the pre-equilibrium approach, you are trying to make sure that the proposed rate law is the same as the experimentally determined rate law. You use the pre-equilibrium approach to reason what the rate law for the equation is when the slow step has a reaction intermediate in it. By using t...

Alexia Joseph 2B

In a steady state approach, a constant intermediate concentration (the d[intermediate]/dt = 0). The pre-equilibrium approach means the reaction before the rate-limiting step is at equilibrium, so you can use the equilibrium constant K. The pre-equilibrium approach is less flexible because it applies...

Alexia Joseph 2B

Yes, if you look at the chemical kinetics outline one of the bullets says "Know how to derive the differential and integrated rate laws for zero, 1st and 2nd order reactions and know how to derive their respective half-life equations."

Alexia Joseph 2B

Are we supposed to be able to know how propose reaction mechanisms?

Alexia Joseph 2B

How do we tell what the units for the rate constant are based on the order of the reaction?

Alexia Joseph 2B

Another example of a zero order reaction is the decomposition of nitrous oxide to n2 gas and o2 gas.

Alexia Joseph 2B

Why is it important theoretically to know what k is/does? What is its relation in terms to the reaction?

Alexia Joseph 2B

How come for both of the half reactions derived from the cell diagram, you add the electron in both cases? Shouldn't the left side of the cell diagram be an oxidation reaction, in which the species loses an electron instead of gaining an electron?

Alexia Joseph 2B

I know that the change in internal energy is equal to q+w (the first law of thermodynamics). Where does temperature come into play with this (specifically regarding isothermal processes)? How come when the change in internal energy is zero, the change in temperature is also zero, but work and heat h...

Alexia Joseph 2B

Why is it false that molecules at exactly 0 degrees Kelvin have no entropy? In theory, isn't the third law of thermodynamics that the entropy of a perfect crystal is zero when the temperature is equal to absolute zero (0 K)?

Alexia Joseph 2B

What equation do you use to find the final pressure after knowing the total volume is 11.0L in #3 of the practice midterm (where delta S was 33.0 J/K)?

Alexia Joseph 2B

Why do we use 5/2 instead of 3/2 for the ideal diatomic gas?

Alexia Joseph 2B

My notes are a little confusing. What exactly is the second law of thermodynamics? I know it has to do with entropy, but what about it?

Alexia Joseph 2B

How do you calculate the degeneracy of something?

Alexia Joseph 2B

From what we learned in class today, I'm assuming we only need to know how to use the equation when delta S and delta H are held constant.

Alexia Joseph 2B

Do we need to know how to derive these equations/the reasoning that's involved to come up with the equations ourselves?

Alexia Joseph 2B

Can someone go over a summary of a situation you should use each Gibbs equation in?

Alexia Joseph 2B

Can someone quickly explain the concept of/meaning of degeneracy?

Alexia Joseph 2B

When you think of an irreversible or reversible process, think in terms of the piston and external pressure example. In one, the system had 2 atm and the Pexternal was 2 atm. In the other, the system had 2 atm and the Pexternal was 1 atm. In the first example, the pressures are at thermal equilibriu...

Alexia Joseph 2B

Can someone explain to me briefly what the second law of thermodynamics is for and why we use it?

Alexia Joseph 2B

The fundamental equation necessary to understand this is that U = q + w (deltas implied)

When there is no work done on the system, U = q

When there is no heat transferred to or from the system, U = w

Alexia Joseph 2B

How do you know that the work is equal to zero while using a bomb calorimeter? like in question 8.53

Alexia Joseph 2B

In class, the example Dr. Lavelle used was with two systems compressed with pistons. Irreversible expansion: will have sudden expansion (results in a large change in volume) Pressure of external atmosphere- 1 atm Pressure of system- 2 atm Reversible expansion: system will change slowly (results a ve...

Alexia Joseph 2B

How can you tell whether or not work was done on the system of if the system did work?

Alexia Joseph 2B

think in terms of where the heat is added or where the heat is released.

endothermic
A+HEAT-> B+C

exothermic

A+B -> HEAT + C

Alexia Joseph 2B

Can someone explain the difference and why it is important to know this property?

Alexia Joseph 2B

Can someone explain how bomb calorimetry works/the main differences as to why it is different from coffee cup calorimetry?

Alexia Joseph 2B

For ICE charts we make, what is the reasoning for why we assume there is little change (so little that it is negligible) if Ka is small?

Alexia Joseph 2B

For the final, should we know toolbox 12.1? I know we didn't really cover acid rain in lecture/discussion, so I was wondering if any actual questions would be asked about the impact of acid rain/chemical reactions that influence acid rain.

Alexia Joseph 2B

Can anyone help explain to me how we are supposed to classify acid strength given something like a group of different acids? I keep reading that for oxoacids, the greater the number of highly electronegative atoms attatched to the central atom, the stronger the acid is, but I don't really understand...

Alexia Joseph 2B

I think that for Chem 14A we are not expected to know Crystal Field Theory, however the basic concept is that ligands as they approach the metal ion experience greater repulsion and cause crystal field splitting. In a d to d transition, an electron in is excited by a photon to another d orbital of h...

Alexia Joseph 2B

Hi I had a question about the work function, specifically from #7 part b on the second quiz that we took. I know we were supposed to use the formula Ek=1/2*m*v^2, but were we supposed to use the work function at all during this part? What exactly is the work function other than being the threshold e...

Alexia Joseph 2B

No, the only difference is the definition. The Bronsted acid is a proton donor, the Bronsted base is a proton acceptor. A Lewis acid is an electron pair acceptor, while a lewis base is an electron pair donor. The Lewis definitions are broader than Bronsted definitions. The Bronsted definitions are m...

Alexia Joseph 2B

An acid donates a proton (H+); once it donates the proton, the remaining species is a conjugate base. A base accepts a proton (H+); once it accepts the proton, the remaining species is the conjugate acid.

Alexia Joseph 2B

Remember that NH3's lewis structure is a central nitrogen atom, attached to 3 hydrogen atoms and with one lone pair of electrons. The molecule is polar because the molecule is not symmetrical. There is a lone pair on the nitrogen, so the dipoles cannot cancel.

Alexia Joseph 2B

The bonds between the C and Cl are polar because there is a large dipole due to the difference in electronegativity, but the molecule itself is nonpolar.

Alexia Joseph 2B

Regions of electron density can be thought of the parts of the Lewis structure where you put either a bond (or multiple bonds) or a lone pair of electrons. If you are thinking about molecular shape and structure, a double bond would count as one region of electron density.

Alexia Joseph 2B

I would assume you should know all the ligands in the spectrochemical series. You should definitely be familiar with the common ligands like water, ammonia, hydroxide, and the halogens.

Alexia Joseph 2B

It's fairly easy to remember the shapes when you classify molecules by their electron domain geometry. Try to visualize the structures Dr. Lavelle showed during lectures to remember the names. Molecules with the same formula have the same general shape (bond angles may differ slightly). For example:...

Alexia Joseph 2B

Basically there is the electron domain geometry and the actual shape of the molecule. The electron domain formula is AX n , where n is the number of domains. The number of domains includes both the lone pairs and the bonded pairs around the central atom. To determine the shape, the same basic concep...

Alexia Joseph 2B

I find that it's the easiest to remember the formula (FC=V-L+S/2), where the number of valence electrons is V, the number of of bonding electrons are S, and the number of lone pair electrons is L. A formal charge of 0 is the most stable.

Alexia Joseph 2B

Yes, radicals are normally designated with one dot next to the element name (in free radical halogenation, the radical is designated by Cl with one dot). A radical is a compound with an unpaired electron.

Alexia Joseph 2B

We do not know the precise location of a particle if it behaves like a wave, and we can't specify the location of a particle with a precise linear momentum. The Heisenberg Uncertainty Principle is meant to explain how we cannot know both location and momentum simultaneously. The equation then hopes ...

Alexia Joseph 2B

Can someone describe more about how to deduce what l and m sub l is when you know what n is? I'm still kind of confused.

Alexia Joseph 2B

Does anyone think we will be tested on scientists in the textbook (Rutherford, Millikan, Geiger, and Marsden)? I know that they had contributions to explaining subatomic particles, but I'm not sure if we will need to know them to explain different properties of electrons.

Alexia Joseph 2B

It's important to understand that the photoelectric effect experiment shined light on a metal surface to try and measure the energy needed to remove electrons from different metals. This experiment was important because it had an unexpected outcome; the experiment showed that unless E(photon)is grea...

Alexia Joseph 2B

In the problem, "A lab technician has made up a 100.0mL solution containing 0.50g NaCl and 0.30g of KCl, as well glucose and other sugars.This question asks that we find the concentration of the chloride ions in the solution. How do you go about solving this problem/what steps do you need to ta...

Alexia Joseph 2B

Should we be rounding w/ significant figures in every calculation in a problem or just in our final answer? My TA told me that we should, but I recalled Dr. Lavelle saying that we only needed to acknowledge sig figs in our final answer.

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