CHEMISTRY COMMUNITY

Andrew Nguyen 3G

Dr. Lavelle mentioned problem solving today in lecture and this is an example of what he is talking about. From what I know, I don't think we learned how to directly solve problems like these in the course reader before. But it makes sense that: [Current] = [Initial] + [Change in initial] So: [O2] =...

Andrew Nguyen 3G

The ethane and methane molecules are substituents of the ether functional group. The reason why the ethane isn't the main "chain" is because the substituent O would have it's own substituent CH3. From what I know I don't think substituents can have their own substituents. Since an ether on...

Andrew Nguyen 3G

Check out page 71 on the course reader.

Andrew Nguyen 3G

There is no negativity difference between the two atoms. However, ethene has an electron rich double bond. The pi bonds extend outwards from the molecule and effects Br2 upon collision. When the Br2 molecule approaches the electron rich area, it causes "induced polarization". The dispersio...

Andrew Nguyen 3G

t1/2 for first order reactions is .693/k or .693 / 6.7×10-4 s-1

t1/2 = 1034.32 seconds, or 1000 seconds for significant figures.

Andrew Nguyen 3G

In that problem, why does adding the two standard cell potentials and their respective half reactions using a Hess' Law approach not work? When added together, we still get U4^+(aq) + 4e- -> U(s) but E equals -2.4 instead of the correct answer.

Andrew Nguyen 3G

It's the metal used as a way to transfer electrons in the battery. Other than that, it doesn't actually react in the reaction itself.

Andrew Nguyen 3G

In terms of the reaction itself, Platinum doesn't "replace" anything, it just serves as a conduit for electron transfer. That's why it doesn't show up on the reaction equation. What happens to the Fe2+? It is the product of the reduction of Fe3+ and oxidation of Cu. The iron remains aqueou...

Andrew Nguyen 3G

It means the redox reaction has reached equilibrium.

Andrew Nguyen 3G

I'm assuming you need to heat both the copper and the water to the same temperature. Because if they weren't, they'd start doing some 2nd Law of Thermodynamics stuff and the water might transfer its heat out to the copper and vice versa. We wouldn't want that to happen on paper, although it is what ...

Andrew Nguyen 3G

For reaction enthalpy, we use kJ only without the /mol. That is because when a reaction proceeds, a certain amount of heat is released or absorbed by the system, which is directly related to the coefficients in the reactants and products anyway. And because the given enthalpy is tied to the coeffici...

Andrew Nguyen 3G

Internal energy = q + w

Not only is energy being put into the system externally, but work is being done WITHIN the system itself, which also adds to internal energy. This is why internal energy is not just delta h.

Andrew Nguyen 3G

A salt with a base will raise pH. Example: CH3COONa breaks up into CH3COO- and Na. Na does not affect pH. Adding in CH3COO- will automatically alter the equilibrium of the reaction: CH3COOH -> CH3COO- + H+ Because more base is added, the reaction favors the reactants and takes away H+ and CH3COO- to...

Andrew Nguyen 3G

Imagine a seesaw. Reactants on left, products on right. Removing something from either side will cause the other side to be heavier and pull the seesaw down. To reach equilibrium, it needs more weight on the lighter side, which represents which side it favors. An imbalance forces the heavier side to...

Andrew Nguyen 3G

Kp uses P instead of brackets by convention. Usually, brackets are used to represent concentration in a solution (Kc), whereas Kp uses P to show partial pressure - that is, the pressure exerted by its constituents. Concentration in solution is different than partial pressure exerted.

Andrew Nguyen 3G

Created by myself while shopping for shampoo.

Andrew Nguyen 3G

If your definition of "ideal" is stability, then yes. Molecules always try to have Lewis structures that are most stable in which the formal charges are as close to zero as possible. Take into account that the sum of formal charges should still add up to the charge of the ionic molecule it...

Andrew Nguyen 3G

If an element has a positive or a negative superscript, it is an ion (Fe 2+, Ca2+, Cl- are some examples). Cations are positive. Anions are negative. These positive and negative characteristics are caused by less or extra electrons.

Andrew Nguyen 3G

For Sc and other d orbitals, we write 3d before 4s because 4s is considered a higher energy level than 3d. Recall that n = 4 is a higher level than n = 3, naturally, but that 4s orbitals are easier to fill in at the beginning.

Andrew Nguyen 3G

Use table 1.9 as described on page 6 to determine what wavelength corresponds to what type of wave.

Andrew Nguyen 3G

It's conventional to report your answer in the units given to you by the question, unless it asks explicitly for you to provide an answer in a specific unit. I think the need to remain in Kg is stressed more in physics, however.

CHEMISTRY COMMUNITY

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Re: Winter 2013 final Q4B

Re: Course reader pg 94

Re: Why is K = kfor/krev?

Re: Question about Exercise 4.25

Re: Calculating Half-life

Re: Textbook Problem #14.27

Re: Pt in SHE

Re: Platinum

Re: Question about batteries

Re: 8.19 part a

Re: Unit Confusion

Re: Problem 8.49

Re: Ions as Bases in CR

Re: Chapter 11 problem 115

Re: Chemical Equilibrium 11.3

Re: Post All Chemistry Jokes Here

Re: Lewis Structures Charges Always Balanced?

Re: Cation Vs. Anion [ENDORSED]

Re: s and d orbitals

Re: Textbook Chapter 1, Question 9

Re: SI Unit Kg