CHEMISTRY COMMUNITY

Deepika Pugalenthi 1A

By solving for the frequency factor by using the Arrhenius equation, what does this tell us about the overall reaction?

Deepika Pugalenthi 1A

Catalysts are on the reactant side of the initial elementary step of a reaction and are used up in following elementary steps. They are produced as a by-product in the following steps. However, intermediates have to be formed first and then only used up in elementary steps of the reaction. The best ...

Deepika Pugalenthi 1A

Catalysts are part of the reactants of the initial elementary step and are used up in following elementary steps. Therefore, the catalyst is not part of the overall reaction since it is used up in the elementary steps. The purpose of the catalyst is to lower the activation energy and speed up the ov...

Deepika Pugalenthi 1A

To find the order of a reactant within a reaction that has multiple reactants, how do make one reactant concentration small and the others large?

Deepika Pugalenthi 1A

Are there other ways to determine the order of the reaction other than plotting to see which leads to a straight line?

Deepika Pugalenthi 1A

To identify the slow step in a series of reactions, do you compare the rate constant of each step or do you have to use experimental data to determine the slow step?

Deepika Pugalenthi 1A

When looking at a graph of the progression of a reaction over time, how do you know when equilibrium has been reached by the reaction?

Deepika Pugalenthi 1A

What information does the rate law help us identify about a certain reaction?

Deepika Pugalenthi 1A

We'll probably get our tests back during discussion sections next week.

Deepika Pugalenthi 1A

When cell potential is positive, it indicates a spontaneous reaction because Gibbs free energy is negative. This is due to the equation for work done, or work max (work max = -charge x E). When incorporating Faraday into the equation, work max = -nFE. Work max equals Gibbs free energy due to the red...

Deepika Pugalenthi 1A

When the reaction is spontaneous, why does cell potential have to be positive?

Deepika Pugalenthi 1A

When calculating standard reduction potential, is there ever an instance when you would multiply or divide the standard reduction potential? Or is it only sign change based on which direction the reaction proceeds?

Deepika Pugalenthi 1A

For what signs of enthalpy, entropy, and Gibbs Free Energy is a reaction spontaneous and when is it not spontaneous?

Deepika Pugalenthi 1A

How is work equivalent to Gibbs Free Energy? Is work done by the system when Gibbs Free Energy is positive?

Deepika Pugalenthi 1A

For the graph Professor Lavelle drew for Gibbs Free Energy in class, the reaction is spontaneous as long as it's approaching equilibrium but not when it is at equilibrium?

Deepika Pugalenthi 1A

For the midterm, do we need to know the derivations of the formulas or do we just have to know how to use them?

Deepika Pugalenthi 1A

what is the difference between reversible and irreversible pathway?

Deepika Pugalenthi 1A

How does an increase in entropy cause gas to expand when delta U is zero?

Deepika Pugalenthi 1A

In class, Professor Lavelle taught three ways to calculate enthalpy. Which method is the most effective and during a test will be told which method to use?

Deepika Pugalenthi 1A

The midterm will be week 6 on Wednesday, February 13, 6-8 PM. You can view the dates for exams on the chem 14B webpage.

Deepika Pugalenthi 1A

The universe is considered an isolated system because the energy of the universe is constant. This matches with the definition of an isolated system, which is that energy is not exchanged with the surroundings, thus staying constant.

Deepika Pugalenthi 1A

When calculating the net delta H using Hess's method, is it required that all the reactants and products be in the same state (liquid, gas, solid)?

Deepika Pugalenthi 1A

Why do work and heat depend on the path instead of the state properties?

Deepika Pugalenthi 1A

When calculating bond enthalpies, what is the relevance of knowing that the entire bond is broken? Is it to understand the conceptual aspect or do the bonds play a role in the calculation?

Deepika Pugalenthi 1A

When making buffers, it's always a weak acid and a salt. To make buffers of varying pH, the only factor changing is the strength of the weak acid?

Deepika Pugalenthi 1A

What is the significance of finding the percentage protonated? Does it help check if the values are valid or plausible?

Deepika Pugalenthi 1A

Think about the million dollar example Professor Lavelle gave during lecture. If a millionaire gives a poor man a thousand dollars, it seems like a lot to the poor man but doesn't seem that substantial to the millionaire. This is due to the fact that a thousand dollars doesn't make a significant dif...

Deepika Pugalenthi 1A

Are pressure and volume inversely related when identifying the direction a reaction is going to go when changing either factor? For example, if I want to increase the pressure, the reaction would move to the side with fewer moles and vice versa?

Deepika Pugalenthi 1A

There is no difference in the formulas for Q and K. The main difference lies in what Q and K are calculated for. K is the equilibrium constant, therefore it can only be applied to identify when the reaction is at equilibrium. Q, on the other hand, is the reaction quotient and can be calculated at an...

Deepika Pugalenthi 1A

In lecture and discussion, it was mentioned that there was activity in reactions but aren't required to be incorporated in calculating the equilibrium constant. Can someone explain to me what exactly activity is?

Deepika Pugalenthi 1A

How does resonance affect the strength of an acid?

Deepika Pugalenthi 1A

When trying to list molecules from weak to strong acid, do we take inductiveness into consideration first or the atomic radii? Does one outweigh the other or is it based on what molecules are being compared?

Deepika Pugalenthi 1A

My TA said there will be questions about oxidation states on the test and that the best way to know them is to memorize the formula in the book. The question on the test will be plug and chug. It would be helpful to know the oxidation states of certain common elements that come up with coordinate co...

Deepika Pugalenthi 1A

When I read that in the book, I thought of heavy and light as referring to the number of electrons the atoms had. The more electrons an atom has (heavier), the larger the radius will be, leading to an increased bond length. And the reverse applies for atoms with a lower number of electrons (lighter)...

Deepika Pugalenthi 1A

Why do transition metals have many oxidation states?

Deepika Pugalenthi 1A

Why do chelating ligands bind cations tightly?

Deepika Pugalenthi 1A

For test 3, we need to know 3.12 and onwards in chapter 3 and all of chapter 4. Professor Lavelle said that as long as we know how to identify the molecular shape and the general angles, we're good. We need to draw Lewis structures, but I don't think you need to know how to draw hybridizations.

Deepika Pugalenthi 1A

In class, Professor Lavelle said that if the 2 carbon atoms in C2H4 rotate, then the pi bond would break. Why would the rotation affect the strength of the pi bond?

Deepika Pugalenthi 1A

Why is the d-orbital required for octet expansion?

Deepika Pugalenthi 1A

Do molecules usually have the seesaw shape when they have one lone pair?

Deepika Pugalenthi 1A

For bond angles, do we only have to know 120 degrees and 109.5 degrees? Is there any formula as to how to determine these bond angles?

Deepika Pugalenthi 1A

Why is it that the shape of the molecule contributes to the strength of interactions?

Deepika Pugalenthi 1A

In class, Professor Lavelle said that increasing the strength of dispersion forces explains why F2 and Cl2 are gases while Br2 is a liquid. What do dispersion forces have to do with the state of these diatomic molecules?

Deepika Pugalenthi 1A

Why do electrons in one atom/molecule cause electron distortion in a nearby atom/molecule?

Deepika Pugalenthi 1A

During the lecture, Professor Lavelle went over the different interactions that give rise to attractive forces? I didn't understand how the dipole-dipole and the dipole-induced dipole interactions worked. Can someone please explain that?

Deepika Pugalenthi 1A

In class, Professor Lavelle said to use the atom with the lowest ionization energy as the central atom in Lewis structures. I think we use ionization energy because it determines the strength of the electrostatic charge and the lower it is, less of a hold it will have on the electrons.

Deepika Pugalenthi 1A

What does the resonance hybrid exactly show? Does it show the attraction of electrons within the molecule through the dotted lines? Thank you!

Deepika Pugalenthi 1A

Electronegativity is how strongly atoms attract electrons to themselves. As you go from left to right, the number of protons in the nucleus increases. Since protons are positively charged and are attracted to the negatively charged electrons, electronegativity will in turn increase as well. Electron...

Deepika Pugalenthi 1A

We don't need to know how to solve wave functions because that goes into double derivatives and some complex math. The main concept you have to know about wave function is how it relates to the quantum numbers. Schrodinger's wave function gives rise to the three quantum numbers n, l, and ml. We just...

Deepika Pugalenthi 1A

How does shielding work and how does that affect electrostatic attraction of the electrons to the nucleus? Thank you!

Deepika Pugalenthi 1A

Valence electrons are the electrons located on the outermost shell, the shell being identified by the principal quantum number, n. In the example you gave for phosphorus, you would consider the valence electrons for the whole energy level of n=3. Phosphorus would have 5 valence electrons. Its n=1 an...

Deepika Pugalenthi 1A

What is the significance of using Coulomb's law in identifying electrostatic charge? What do you do with the values that you obtain from the equation? Thank you!

Deepika Pugalenthi 1A

During the lecture, he said that all quantum material would be covered on the upcoming test. Since he did slightly touch on electron configuration in lecture, I would say to study it to be safe and prepared for the test.

Deepika Pugalenthi 1A

What does it mean when the electron-density distribution is symmetrical versus non-symmetrical? Thank you!

Deepika Pugalenthi 1A

During lecture, Professor Lavelle was saying that any wavelength smaller than 10^-18 cannot be seen. What does it mean for a wavelength to be seen? Thank you!

Deepika Pugalenthi 1A

Why do photons give off only positive energy?

Deepika Pugalenthi 1A

s^-1 and Hz can be uses interchangeably because they are the same thing. Usually, in problems it is given in Hz so I would recommend using Hz instead of s^-1.

Deepika Pugalenthi 1A

Why do we have to use 100 grams as the starting point when trying to find the empirical formula? Thank you!!

Deepika Pugalenthi 1A

I'm confused about when to count the zeros as significant figures and when not to. Can somebody please explain this concept to me? Thank you!

Deepika Pugalenthi 1A

I use scientific notation primarily when there's multiple zeros after the decimal point before getting to the exact numbers. For example, if the answer is 0.00072, I would write it in scientific notation instead of writing out all the zeros in order to get two sig figs.

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