CHEMISTRY COMMUNITY

Schuyler_Howell_4D

Do we need to know enzyme kinetics for the final?

Schuyler_Howell_4D

Why did they use Ea,cat=(75/125) instead of Ea,cat=(125-75) to help find the factor by which the rate of the reaction changed?

Schuyler_Howell_4D

Can someone explain where they got the equation they use to solve for Ea:

ln(k'/k)=(Ea/R)[(1/T)-(1/T')]

Schuyler_Howell_4D

Hi, did anyone go to today's review session (Mar. 9, 12-2pm) and would be willing to post the notes/practice? I really wanted to go but woke up very sick. If you could help a girl out you'd be the MVP of the day!

Schuyler_Howell_4D

Here you go :)

Schuyler_Howell_4D

I think so. If you expanded it to be k[A][A] then you would be able to find that A could be two different reactants.

Schuyler_Howell_4D

The unique raate of the reaction can be solved for using this formula: -(1/a)(d[a]/dt) Conceptually it is average reaction rate adjusted for the stoichiometric coefficient so that the consumptions of each product and reactant are equal. "Unique reaction rate is the average reaction rate divided...

Schuyler_Howell_4D

Another question that goes off of this is, can you have an order be a fraction or do they have to be whole numbers?

Schuyler_Howell_4D

Okay, I know this is a pretty basic question but, I think it is the source of all my confusion. What is kinetics used for and why do we care? I get that it has to do with reaction rates but are we just finding how different variables affect the reaction?

Schuyler_Howell_4D

Why does -Wsys= Wmax in reference to Gibbs free energy?

Schuyler_Howell_4D

Could it be that you have to balance oxygen with water so you then have to balance the newly added hydrogens for acidic solutions? And then in the basic solution, you balance the hydrogen by adding water and then have to balance the newly added oxygens?

Just an idea

Schuyler_Howell_4D

Delta G is negative for a spontaneous reaction.

Schuyler_Howell_4D

Delta G^o is the standard free energy change based on standard state formation of 1 mol of the substance. Delta G is the free energy change of the substance not in the standard state.

Schuyler_Howell_4D

He used 0 for Gibbs Free energy to find the critical point at which the liquid and gas phase both exist. At this temperature deltaG is zero so, a temperature higher than the critical temp found will be spontaneous because deltaG is negative. A temperature lower will mean a positive deltaG so the rev...

Schuyler_Howell_4D

Rotational would be around an axis, think of it making a circle. Vibrational is just back and forth on one axis, think of walking back and forth on a line.

Schuyler_Howell_4D

For #6, if heat is negative and therefore losses heat why is the reaction endothermic?

Nevermind I don't know why I put a negative there. I know heat is positive now.

Schuyler_Howell_4D

For #6, how do we know that work is equal to 0? I was wondering the same thing. What I came up with was that is you use pv=nrt to find deltaV then you can see that since pressure, temperature, and R are constant the change in volume will depend on the change in moles. The equation has a 1:1 ratio f...

Schuyler_Howell_4D

Are bond enthalpy and bond energy the same thing? If not what is the difference?

Schuyler_Howell_4D

This just means that a large difference in W will only result in a small change in S.

Schuyler_Howell_4D

Residual entropy is the difference between entropy not at equilibrium and the state that the molecule is closest to zero (temperature). It is just a way to measure entropy which is ultimately a way to measure work.

Schuyler_Howell_4D

I'm currently in physics 5B and for phase changes, we used similar but different equations for phase changes and temperature changes. I was just curious how they relate to each other (other than the fact that they are for the same concept). Physics Equations: - For phase change: mL (m is mass and id...

Schuyler_Howell_4D

If you think about something that is very hot, like a cup of coffee, and you put it on a room temperature table does it stay hot when you come back to get it after an hour or two? Objects want to reach equilibrium and that includes thermal equilibrium. As the coffee sits out the heat (which is the t...

Schuyler_Howell_4D

In a reversible reaction, the reactants can for the products and the products can also produce the reactants.

In an IRreversible reaction, once the products are formed through reactions they cannot form the reactants because they are reacting to form other products.

Schuyler_Howell_4D

In response to the question about dry ice, it is special in the way that carbon in the form of dry ice goes directly to a gas phase and doesn't become a liquid. Sublimation occurs because the phase change happens at temperatures and pressures that can't allow the compound to be liquid. It requires a...

Schuyler_Howell_4D

Pretty much. You can add (or subtract) equations together to get the desired reaction that you need the enthalpy for. Once you have decided what needs to be added or subtracted you use their enthalpies, making sure the signs match if that equation is endo- or exothermic.

Schuyler_Howell_4D

Is it possible to have an end result of the ice table that gives you only an x in the numerator and the quadratic equation is on the bottom? I have been looking at a problem over and over to make sure I wasn't making a mistake. If it is possible how do you use algebra to solve for x. If it isn't wha...

Schuyler_Howell_4D

If you are finding the pH or pOH, the best place to start is to figure out if it will produce H3O or OH. Once you know that you can figure out if you are missing an element that would have to come from water. If it is an acid you will most likely always have to add water to write out the equation, f...

Schuyler_Howell_4D

What is the full relationship between pH and pKa?

Schuyler_Howell_4D

The best place to start is to go through the homework for outlines 1 and 2; anything you needed to do the homework with is what you'll need to know. The big ones being: Kc= ([C]^c*[D]^d)/([A]^a*[B]^b) Kp= ((PC)^c*(PD)^d)/((PA)^a*(PB)^b) P meaning partial pressures pV=nRT Q=[P]/[R] for reactions not ...

Schuyler_Howell_4D

What chapter is the question you have in?

Schuyler_Howell_4D

Can someone explain when you should use variables such as X in an ICE table versus finding the change based on stoichiometric coefficients before being plugged into the table? In one of the Audio-Visual Learning Modules (I think equilibrium part 2) Dr.Lavelle went ahead and used mole ratios to find ...

Schuyler_Howell_4D

First, you have to physically count the individual molecules that are single and the molecules that are still bonded to find the moles of reactants and the moles of products. Once you have those values you multiply them by 0.1 because that is the partial pressure given to you in the problem and you ...

Schuyler_Howell_4D

Can you clarify please because if you calculate Q the same way you calculate K how can they be different values?

Schuyler_Howell_4D

Even though there is a difference of electronegativity between C and H, why do we ignore it and say there is no dipole moment? Is it because it isn't significant enough?

Schuyler_Howell_4D

In a review session, the LA said that if they ask for the composition of the bond then you determine it for the sigma bond and pi bonds separately. The textbook shows them together. What is right/ how do you determine the coefficient for composition?

Schuyler_Howell_4D

How do you write a neutralization reaction if they give you the product? How do you decide what acid/base to use?

Schuyler_Howell_4D

They are a way to examine compounds with transition metals. They have biological significance, think about the chemotherapy example Prof. Lavelle used in class.

Schuyler_Howell_4D

Be able to fully name compounds is the best way to make sure you are ready for the final. There are good example questions in the book to help you.

Schuyler_Howell_4D

From what I understand they do. An acid will gain an electron pair and donate a proton. An oxidizing agent gains electrons, so I think you can say an acid is an oxidizing agent. A base is a proton acceptor and donates electron pairs. A reducing agent loses electrons, so I think you can say a base is...

Schuyler_Howell_4D

Yes, they are the same thing. The difference is just what characteristic of the molecule you are using to define it as an acid or base. A Lewis acid is a molecule that accepts electrons, a Bronsted acid is a molecule that donates a proton. An acid will have both of these characteristics. H2SO4 is an...

Schuyler_Howell_4D

As I understood it the sigma bond doesn't become a pi bond, it is that a sigma bond is there and a pi bond is added next to it. Is this right?

Schuyler_Howell_4D

Pi bonds have electron density on either side of the internuclear axis. This means that because of electron repulsion and the regions of electron density formed by the already present sigma bond, the electrons are "locked" into a region where they can remain. There is no room for the elect...

Schuyler_Howell_4D

Hybridization is important for bonding. You "mix" the orbitals together to visualize and determine how any valance electrons area available for bonding.

Schuyler_Howell_4D

When the regions of electrons fluctuate in a molecule (call it molecule A) this changes where the dipole interaction with another molecule (call it molecule B) is "located". Since electrons aren't really stationary they cause the region of partial charge to shift back and forth a bit. When...

Schuyler_Howell_4D

When there are no partial charges on any of the atoms, then the molecule will be non-polar (hence no dipole moments). The molecule can still be non-polar if the negative charges on an atom are canceled out by a positive charge on another atom (when the dipole moments are canceled out). To cancel out...

Schuyler_Howell_4D

The reason you can't have two sigma bonds is because of the orientation of the regions of electron concentration. There is always electron repulsion and since a pi bond can't have a rotation, the atoms/ molecules are locked in a specific position. Once a pi bond is used, the following bonds have to ...

Schuyler_Howell_4D

Yes, the molecule obeys the octet rule, however, phosphorous can have an expanded octet in other instances. Start by connecting all of the P to each other (literally make sure each P has a line to all the rest). Then apply the valence electron rule, where you make sure you have the correct number. Y...

Schuyler_Howell_4D

I also have a follow-up question to this... In class, we talked about how those forces would be interchangeable with dipole-induced dipole interactions. Does this mean they are the same or for sake of simplicity we treat them the same way?

Schuyler_Howell_4D

Common elements that can have an expanded octet are sulfur, phosphorous, silicon and chlorine. They can have more than an octet because they have d- orbitals that can hold electrons. These d-orbitals have higher energy than 4s- orbitals so those electrons are used for bonding. Here is a helpful link...

Schuyler_Howell_4D

The post can be a question you need to be answered about the material, a reply/ answer to someone's post, or a helpful resource. I think if it is a question that is a logistic question (like this one), it may not get points but, double check with your TA about that.

Schuyler_Howell_4D

I think so. If I understand correctly, everything up to and including Wednesday's lecture (but not Friday's lecture).

Schuyler_Howell_4D

General steps: 1)Convert grams of each element into moles of the element 2)Take moles of each element and multiply by the ratio of that element in the molecule (1 C/ 1 CO2) so that you get grams of the individual element 3) Take those grams from step 2 and convert from grams of the element to mols o...

Schuyler_Howell_4D

A coordinate covalent bond is an example he used in class where H2O is bonded and the electrons are being shared between the H and O but, once they break apart the O is left with 6 electrons and the H are each left with one. In short, the one atom donates both electrons in a bond.

Schuyler_Howell_4D

Are you referring to Lewis Structures? If so, I think it is whichever one is more electronegative as long as you apply the valence electron and octet rule correctly.

Schuyler_Howell_4D

You want the Lewis Structure to have the least amount of charges on each atom. If there are charges on specific atoms in the molecule then you want it to be a low number. Here is a video I found helpful: https://www.youtube.com/watch?v=r9Hc71xPMPs This person also does some other videos that were a ...

Schuyler_Howell_4D

Ligands are molecules or ions that have one or more pairs of lone electrons. They typically bond to things that have a positive charge. They are classified by how many pairs they have. The Lewis structure will be a more thorough way to check the pairs of electrons because you have to draw it out and...

Schuyler_Howell_4D

Energy will increase because it is dependent on n (n increases). n increases from 1 to 2. l increases because it is dependent on n as well (l can be 0 to n-1). The radius of an atom is a function of n ( as you increase the " electron shells" the wider the atom) so it also increases. Think ...

Schuyler_Howell_4D

Also, the orbitals are actually math functions that show the probability of finding an electron in that space (shape).

Schuyler_Howell_4D

Once you use the equation: E=hc(lambda)^-1
you will get energy in joules per photon. You then multiply that by 9.8 x 10^20 which is the number of photons.

(You should get 450 J. )

Schuyler_Howell_4D

Why do we use $p=h*\lambda ^-^1$
instead of $\lambda =c*v$ to find the velocity of a neutron?

Schuyler_Howell_4D

There is not a way to calculate intensity/ amplitude using that formula as far as I am aware. If you were looking for a formula to find intensity you may want to use this one: light intensity is proportional to 1/ distance squared (distance being in meters from light source) Also, the relationship b...

Schuyler_Howell_4D

The energy of a photon is determined by the equation hv . This energy is absorbed by the electron that is either ejected (if the energy of the photon is greater than work function) or remains. A key thing to understand that may help answer your question is that the equation (1/2)m e v 2 = hv- work f...

Schuyler_Howell_4D

Oscillations of the electric and magnetic field are the wave that light travels in. The oscillation can be measured by using amplitude and wavelength. Amplitude: height up and down of the peak from the middle (see figure 1.7) can be squared to find the intensity of the light (radiation) Wavelength (...

Schuyler_Howell_4D

Do you think we convert each compound to moles and then just find percent composition?

Schuyler_Howell_4D

More specifically, take the volume you would like to prepare and multiply that by molarity (moles/liters) which should give you moles. Once you have moles, multiply by the molar mass of the compound (found from adding up the atomic masses). This gives you grams needed to create the solution. If you ...

Schuyler_Howell_4D

The previous reply is correct. For that question, the net number of moles is 4 because you add up the moles on the left side of the equation (reactants) and then subtract that from the total number of moles on the right side of the equations (products). Follow up question: If there is a net gain the...

Search found 66 matches