CHEMISTRY COMMUNITY

Parth Mungra

There are also different forms of this equation, but they all have similar derivations

Parth Mungra

the k value for the psuedo system will incorporate something similar to k=k1k2/k2, and these k1 and k2 come from the molecules in large excess.

Parth Mungra

No, a positive E supports G being negative, as can be seen with the equation dG=-nfE

Parth Mungra

For zero order, there is no half life due to the integrated rate law not having concentration

Parth Mungra

With this question, you have to use the vant hoff equation. The question gives the unknowns except for K. You can solve for K, and they put that back into the original balanced equation and solve for conc of h30+

Parth Mungra

I think we would be asked to draw them in accordance to their steps, meaning a slow step will have a different looking trough than a fast step.

Parth Mungra

Not always. wmax is refers to dG, as it is the maximum energy that is free to do work. Likewise, this is the same with cell potentials.

Parth Mungra

No, standard conditions do not imply that only one electron is being transferred. You should complete the half reactions and see the moles of electrons transfered.

Parth Mungra

What is a mechanism? How does this affect the rate laws? Also, what can affect it?

Parth Mungra

Do you include water in a cell diagram? What is it is in a gas phase, do you then include it?

Parth Mungra

You do not need to work backward from part c. You can find the average change in rate (part a) by dividing the change in concentration by the change in time. Part B is asking about ratios of rates, which can be found by looking at stoich. coefficients. Thus, you can find part c based on these coeffi...

Parth Mungra

The gas product will leave the solution (not all of it however, this is why the reverse reaction can still occur), and thus there is less product to react to form reactants

Parth Mungra

What are the units for rate? Also, what are the units for the n or m values in the differential rate law?

Parth Mungra

To build off that, we talk about the initial rate of the reactants going to the products only, and not the reverse reaction. This makes our analysis and our calculations nicer.

Parth Mungra

dG= the maximum amount of work that can be done.

Parth Mungra

Gibbs Free energy helps us calculate the energy that is free to do work after a certain process. This does not include the energy in between electrons or protons, but it is the energy that can be transferred to do, for example, expansion against a force.

Parth Mungra

Remember that dG represents all the energy (from a process) that is free to do work. Essentially, this statement is saying that virtually all of the free energy calculated from the Gibbs Free Energy equation is available to do work (the maximum amount)

Parth Mungra

If K=0, then the reaction is neither spontaneous nor nonspontaneous

Parth Mungra

You can look at the equation as well, dG=dH - TdS
If the entropy expression is greater than enthalpy, then the reaction will be spontaneous (exergonic), because dG is negative.

Parth Mungra

Gibbs free energy represents the total energy that is 'free' after a reaction. The energy from electrons and electrostatic charges are not included in this 'free energy.' Free energy is energy that can be used to do work.

Parth Mungra

In lecture, Dr. Lavelle said that the thermodynamic property resulted in a small error in entropy. What does thermodynamic property mean and how does it result in a small error in entropy when using Boltzmann's constant formula?

Parth Mungra

X represents the number of locations that the atoms (the number of atoms is n) can be in.

Parth Mungra

For most liquid and aqueous solutions (not gases) dU=dV=qp because there is no change in volume, and thus no change in expansion work. w=0 is when they are equal.

Parth Mungra

We want an intensive property because it can help us more with our specific experiments or reactions. We can divide the Heat capacity by the amount of substance in grams to get the specific heat capacity, which is an intensive property. We can also divide the heat capacity by the moles of substance ...

Parth Mungra

I am a bit confused on the piston problem. Does the external pressure on the piston cause work to be done, which then causes displacement? I don't understand how applying downward force causes the distance part of the equation (w=PAD).

Parth Mungra

Well, the external pressure can be taken out of the integral, and then you are left with w=Pex (Integral from vintial to vfinal of 1 dv). This integral part just equals vf-vi, or delta v. It's the same thing as the previous equation we learned.

Parth Mungra

If you wanted to find the total amount of hydronium ions, you add the hydronium produced from the H2So4 and the ones produced by HS04-. H2S04 dissociates completely but HS04- is a weak base.

Parth Mungra

Does using ICE table only work for finding concentrations at equilibrium? Essentially, can you use the ICE table for Q?

Parth Mungra

If you are trying to write an equilibrium constant for a rxn where all the products are solids, would this mean that the entire reaction has no equilibrium constant? Or would it be 1/[r]?

Parth Mungra

Kw is just the Equilibrium constant for water, which undergoes autoprotolysis, a natural reaction (very few water molecules do this). By doing this, there is a concentration of hydroxide and hydronium ions. If you take the Kc of this reaction, you find Kw, which is 10^-14 at 25 degrees Celsius

Parth Mungra

pKa + pKb equals the pKw, which is usually 14 (Kw= 10^-14) at 25 degrees Celsius. This is true if you add more acidic reactant or basic reactant because of the inverse relationship between the two. Ka x Kb involves canceling out concentrations of molecules and ions, so you end up with [H30+] x [OH-]...

Parth Mungra

x is negligible when the acid/base reacting with water is weak, meaning very little will dissociate into ions. Therefore, we consider this change in concentration (x) from initial to final to be so small that it can be negated.

Parth Mungra

What's the difference between the two? They are calculated the same way, but Kp doesn't include reactants/products in the aqueous/solid state?

Parth Mungra

It was meant to be in comparison to K. A Q<K means more products, and Q>K means more reactants. Q can be calculated at any time during a reaction.

Parth Mungra

Q is the reaction quotient, and this determines which direction a reaction will proceed during a given moment. You can calculate Q by taking the concentration of the products over the concentration of the reactants. If Q>K then forward reaction is favored and more reactants. If Q<K, then the reverse...

Parth Mungra

I was doing some problems from the homework set and I was confused when some problems used the suffix -ate. In 6th ed, Chp 17 number 29 c, the formula is [Co(CN 5 )(OH 2 ) 2 ] 2- . The name in the solutions manual is Aquapentaacyanocobaltate (III). I was wondering why the cobalt atom was called coba...

Parth Mungra

En stands for enthylenediamine. It is a didentate, meaning it can form two bonds to the central atom.
edta stands for enthylenediaminetetraaceto, and this is a hexadentate, forming 6 bonds to the central atom.

Parth Mungra

You have to look at the charges and the amount of atoms/molecules inside the coordination compound as well as outside. If there is a Cl 3 , then the entire molecule has a -3 charge. Look at the others and then fill out the charge for the transition metal. That should be your last step. Make sure the...

Parth Mungra

The above answers are correct; bromine is bigger, therefore forming a smaller, weaker bond, allowing the bond to be broken easier. For the salt part of your question: If you have NH4+, for example, this will give a proton (an H+) because then it can form to a NH3. This extra proton will then form a ...

Parth Mungra

You cannot find the exact answer. It's something you have to google. However, drawing the lewis structure can tell you if it is less than 120, or 120 or whatever. You won't find the exact number but it will you give an idea of the compound you are looking at.

Parth Mungra

The bond angle between the C-O-O bond is stated to be 109.5 degrees in the solutions manual. I was confused because I thought this was less than 109.5 degrees due to the two lone pairs on the oxygen.

Parth Mungra

If you look at the vectors of each dipole moment created between the N-O interaction, they end up canceling. The vertical aspect of one N-O will cancel the others.

Parth Mungra

How are pi bonds weaker if they are double/triple bonds? If they hold atoms side by side, doesn't that mean they are stronger since they cannot rotate?

Parth Mungra

Hybridization is experimentally observed. It explains how atoms, like Carbon, form bonds at the orbital level. It was observed that the orbitals mix to create something we call hybrid orbitals.

Parth Mungra

I think the characteristics are dependent on the atoms and the atoms they interact with. For example, in covalent bonds, not all of the electrons are shared equally, due to electronegativity differences, giving the molecule some ionic properties. Other molecules might not have this characteristic, b...

Parth Mungra

In terms of energy It would be in between the energy levels of the s p and d orbitals, just as how 2sp is in between s and p.

Parth Mungra

What are axial bond angles and how do they differ from regular bond angles?

Parth Mungra

Water, which it has hydrogen bonds, has a higher melting point because of the interactions between the molecules. The Oxygen's of each molecule has a slight negative charge and this has an intramolecular attraction with the Hydrogen of another water molecule. So, this attraction means it takes more ...

Parth Mungra

Those are the dissociation energy values for specific bonds between two atoms. This is the energy needed to break a bond. Ions have higher dissociation energy values while Induced Dipole Induced Dipole are lower. These values are always positive.

Parth Mungra

When describing the Van der Waals interactions, Dr. Lavelle said that these interactions are always present and always positive. What does this mean?

Parth Mungra

Dipole-Dipole interactions are different than induced dipole-induced dipole interactions in that Dipole-Dipole interactions involves one atom, that is bonded to another atom, having a high electronegativity, thus creating a polar molecule. The atom that is pulling on the electron more has a slight n...

Parth Mungra

Bond lengths are going to be given. For example, a problem might tell us the bond length is 1.75 angstroms and we can use that to help obtain more information.

Parth Mungra

Do ions with a greater electronegativity difference have more polarizability? So, NaF bonded, there would be more distortion due to the F atom having a much higher electronegativity than Na, creating an unequal electron distribution, correct?

Parth Mungra

If EN is a measurement of electron’s strength, then why are there no units for EN?

Parth Mungra

No, we only have to know what we have covered up to and including Wednesday's lecture.

Parth Mungra

For many atoms, you can observe their position in the periodic table and their valence electrons. Fluorine, for example, has 7 valence electrons, 2 in the 2s subshell, and 5 in the 2p subshell (2 in the 2px, 2 in the 2py, and 1 in the 2pz orbitals). Because of this, it needs to gain an extra one ele...

Parth Mungra

This is for clarification: we can never fully know the structure of a resonance hybrid, correct? It has average bond lengths, but with the electrons being delocalized, there's no way to know. Am I missing something?

Parth Mungra

The atom with the lowest ionization energy and the lowest electron affinity is the central atom.
Some tips: If there are carbon atoms in an organic molecule carbons are most likely going to be the backbone of the lewis structure, but not always. Hydrogen will almost never be the central atom.

Parth Mungra

A +1/2 is a spin up, and a -1/2 is a spin down. I don't know to what extent we will use this, but when you are filling an Aufbau diagram, make sure to follow to Pauli Exclusion Principle and Hund's Rule. When filling it out the diagram, start with any spin, I do not think it matters. Electrons want ...

Parth Mungra

Yes, but there is more orientations for the d subshell. There are 5: dyz, dxz, dxy, dx^2y^2, dz^2. Once you call one plane x or y or z, make sure you stick with them otherwise your orientations will overlap.
Hope that makes sense

Parth Mungra

I understand that if the energy of the incoming light does not match the energy required to excite an electron to n=2 or n=3 or whatever number (assuming n=1 is the starting position of that electron). What if the incoming light has enough energy to excite an electron to n=2.5? Because electrons can...

Parth Mungra

In the beginning of Wednesday's lecture, we went over that we have a math model that represents a wave function. I was confused on how we went from the wave function to the probability of finding the electron just by squaring the original math model. I'm confused because squaring a function changes ...

Parth Mungra

Part A asks for the wavelength and you can substitute the momentum formula (p=mv) into the de broglie formula (wavelength=plancks/p) because you have the mass and the velocity of the electron. So it should look like this: Wavelength= (Planck's constant)/(mass x velocity) You don't need the kinetic e...

Parth Mungra

I was doing a problem in the 6th edition textbook (Chapter 1, 59), and I was confused on how to get energy per photon. It involved using the De Broglie equation, but I don't know how to obtain the correct units because they do not cancel at the end.

Parth Mungra

What's the difference between the description of ray vs light? Ex. Gamma Ray vs Ultraviolet light
I'm sure we won't need this information, just curious.

Parth Mungra

I had a similar question to yours. During our Monday lecture, Dr. Lavelle said that we don't know what light looks like, but we have these two models. I'm confused as to why we keep using the classical wave model if we have found an experiment that shows the wave model is not correct. Why don't we u...

Parth Mungra

You are correct about intensity and energy of photons. The intensity of a photon determines how many photons there are. A strong, intense light will be able to bounce off more electrons from the sheet of metal because there are more photons, and each photon interacts with one electron. Higher energy...

Parth Mungra

I was a bit confused on why electrons cannot flow from one energy level to the next. What's stopping them from going on a continuous path through each level, and why do electrons need to jump energy levels?

Parth Mungra

I was reading through the section on Molarity (G). The textbook stated something about "we use molarity of solute, not molarity of solution." I do not really understand this because I thought molarity was the same for both. Can someone help explain the difference?
Thanks

Parth Mungra

In the reaction it takes 2 moles of water for every 1 mols of calcium carbide. The problem was given with information that will let you get 1.56 mol of CaC 2 and 5.55 mol of water. Because of the 1:2 ratio, we have to check to see how many mols of water molecules will be used with the given amount o...

Parth Mungra

It can be viewed as either. Breaking it down by viewing it as atoms can make it simple to understand the reaction, but looking as the coefficients as moles makes mass percent composition easier to understand because the amu of each element is in grams per mole.

Parth Mungra

Everything the people said above me is correct: You cannot lose or gain mass in a chemical reaction. I know we are not at nuclear reactions, but this the law of conservation of mass only applies to chemical reactions. We can use combustion of propane (C 3 H 8 ) as an example of a chemical reaction. ...

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