CHEMISTRY COMMUNITY

Justin_Yi_1J

Dear Dr. Lavelle, Thank you so much for providing all these chemistry resources to us. You have worked tirelessly for us and I truly apprecitate all the thought you put into everything you have done for our class. Despite the challenges in your personal life, you made the class an amazing experience...

Justin_Yi_1J

An approach to this is looking at the formula for rate constant, k = Ae^{\frac{-Ea}{RT}} = \frac{A}{e^{\frac{Ea}{RT}}} . We see that the rate constant can never equal 0. So, if we see a very small rate constant, we can say that the reaction does not occur. In the question, we are given the values fo...

Justin_Yi_1J

In order to bring reactants together to undergo a chemical reaction, energy must be put into the system to do the work necessary to perform the reaction. Gibbs free energy is a measure of the energy in a system that is available to do work. A system must gain energy to do the work of the reaction, s...

Justin_Yi_1J

for number 8 on Quiz 3, I'm not understanding why Br2 acts as an electrophile. Can someone explain please? The reason Br 2 can act as an electrophile is due to electron-electron repulsion. Typically, Br 2 is a non-polar species. However, when it encounters the pi electrons of an alkene at a high en...

Justin_Yi_1J

There are four ways to tell that Lavelle has given: 1. It is given (e.g. this is the slow step) 2. The rate constant for one reaction is larger than the other. k 1 >> k 2 means the first elementary step is faster than the second. 3. The step with the most amount of bonds broken is the slow step. Thi...

Justin_Yi_1J

A way to think about it is using the equation ΔG° ‡ = ΔH° ‡ - TΔS° ‡ . Since a catalyst/enzyme will place the substrates into a more ordered state so that the substrates can more readily react, ΔS° ‡ will be higher with a catalyst than when there is no catalyst present. When ΔS° ‡ is higher, ΔG° ‡ l...

Justin_Yi_1J

An R is a generic alkyl group substituent. So for example, an alkane of length n might be expressed as having an R group attached to one of its carbons. In the case of something like 2-methyl-pentane, the R is the methyl group on the 2nd carbon. Methyl is methane with a removed H, allowing it to bon...

Justin_Yi_1J

If the mechanism is a slow step followed by a fast step, then the rate law of the slow step is the overall rate law. However, we must go through a different processes if the initial elementary is not slow. That is because any elementary step after the initial step will have an intermediate. So a slo...

Justin_Yi_1J

We will most likely be given the information that the reaction goes through multiple steps. It is not like we will be asked to know exactly what steps the reaction has if we are just given the chemical equation. We will either be given a mechanism or given enough information that writing a mechanism...

Justin_Yi_1J

The integrated rate law is useful for finding the concentration after a certain time if the initial concentration and the rate constant is known. The integrated rate law can be found by getting the specific solution to the separable differential equation \frac{\mathrm{d} [R]}{\mathrm{d} t} = \textup...

Justin_Yi_1J

It has to do with the kenetics of the reaction. Lavelle said in lecture the first day of kenetics the example of the diamonds turning to graphite. The reaction has a negative Gibbs Free energy, but it never occurs in real life.

H2 and O2 to H2O is a similar case.

Justin_Yi_1J

I just reread the question and noticed the second half about what metal to use. Select a metal that does not easily react but conducts, such as platinum or gold for example.

Justin_Yi_1J

You need to use an inert electrode when the species that you are having in the redox reaction is not a good conductor of electrons. For example, when using hydrogen gas, the gas can be in contact with an inert electrode of platinum metal. The metal will conduct the electrons to or from the hydrogen ...

Justin_Yi_1J

Yes, you must raise both sides of the equation to the e power to cancel out the natural log.

Justin_Yi_1J

What the relationship S surr = - \frac{Hsys}{T} is saying is that as the system becomes more ordered, the surroundings must be getting more disordered. S = \frac{Hsys}{T} , as we learned in class. The equation basically is proving the 1st law of thermodynamics which says the total internal energy of...

Justin_Yi_1J

To hydrogenate it means to add hydrogen to the molecule. You see in the given reaction H2 is added to the C2H2, making it C2H2. The pi bond breaks between the carbons and the electrons pair with the hydrogen diatomic molecules that also have their bonds broken.

Justin_Yi_1J

Yeah that is the correct reasoning. Work is done by change in volume and one way to change volume is by changing the amount of moles.

Justin_Yi_1J

This is because it is a weak acid and it only partially disassociates, that is the majority (about 100:1 according to Lavelle) stays as the acetic acid. This is because the Ka is small, so the products (the conjugate base and a proton) are far less than the acetic acid. One reason why the acid favor...

Justin_Yi_1J

The strength of an acid also has to do with its conjugate base anion's stability. If the anion is more stable after the loss of a proton, the acid is more likely to disassociate. In that case of strong acids, the loss of a proton creates a monoatomic anion, which is very stable and therefore it dona...

Justin_Yi_1J

When expansion or compression occurs, the system will try to minimize the change. If it is compressed, the pressure increases. To counteract this, the system shifts to the side with less moles of gas in order to minimize the change in pressure. Vice-versa for expansion.

Justin_Yi_1J

This is because the difference in energy of the subshells of each of the atoms will cause the pi molecular orbitals to be lower in energy than the sigma molecular orbital. The interaction between the sigma and pi orbitals will cause the pi to be a lower energy state. I believe it has something to do...

Justin_Yi_1J

The key thing your response did not touch on is the fact that each photon corresponds to a singular measure of energy, in other words light is quantized. You mentioned a photon is a particle and has wavelength like a wave, but in order to make the leap to quantized energy you must state the frequenc...

Justin_Yi_1J

Splitting energy is the difference in energy between the bonding and antiboding states. It is represented by the distance between the two states in the MO diagrams.

Justin_Yi_1J

I do not believe you would need to know the exact numerical values, just a sense of the trend.

Justin_Yi_1J

In general, the molecular formula should not affect the Lewis structure. For example, writing CO 2 or, going against convention, O 2 C would not change the Lewis structure for the molecule. The central atom is still C because it has the higher electron affinity in this case. The only time the formul...

Justin_Yi_1J

So if I understand you correctly, the objective of part c is to find the wavelength of the light that causes the emission of the electron. So in order do this, take the energy you found from part b. This is the threshold energy or work function. The energy of the absorbed photon that caused the elec...

Justin_Yi_1J

So the first step in using the information gathered in step A to answer part B is to see if the empirical formula (SnO 2 ) is the same as the molecular formula, and if not, find out what the molecular formula is. To do so, we must find the mass of the sample contained in the crucible. This is found ...

CHEMISTRY COMMUNITY

Search found 27 matches

Re: Saying Thank You to Dr. Lavelle

Re: HW #4.40

Re: Standard Gibbs Free Energy of Activation

Re: QUiz 3

Re: Rate Determining Step

Re: Catalysts/Enzymes regarding Entropy

Re: "R" in Reference to Alkane to Alkyl Naming

Re: Slow and Fast Steps [ENDORSED]

Re: Knowing the number of reaction mechanisms

Re: Differential Rate Law Versus Integrated Rate Law

Re: If gibbs free energy of formation for water is negative, why is the formation of water not spontaneous?

Re: Inert electrodes?

Re: Inert electrodes?

Re: Van't Hoff Equation

Re: Gibbs Free Energy Equation Related to S(universe)

Re: HW 8.57

Re: 8.93 Substituting PdeltaV=nRT into w=PdeltaV

Re: molecular form

Re: Strong Acids

Re: Difference between Pressure and compression/expansion?

Re: heteronuclear diatomic molecules

Re: Question 3B on the Fall 2016 Midterm [ENDORSED]

Re: Splitting Energy

Re: Quiz 2 Question 1 Wording [ENDORSED]

Re: Order or formula

Re: Question 1.33 (c) from the textbook [ENDORSED]

Re: Review Principal L39