Search found 22 matches

Wed Mar 15, 2017 5:45 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Winter 2013 final Q4B
Replies: 3
Views: 476

Re: Winter 2013 final Q4B

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] =...
Tue Mar 07, 2017 10:24 pm
Forum: *Ethers
Replies: 2
Views: 798

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...
Tue Mar 07, 2017 10:13 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Why is K = kfor/krev?
Replies: 3
Views: 774

Re: Why is K = kfor/krev?

Check out page 71 on the course reader.
Wed Mar 01, 2017 9:57 am
Replies: 1
Views: 347

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...
Wed Feb 22, 2017 1:50 am
Forum: First Order Reactions
Topic: Calculating Half-life
Replies: 2
Views: 644

Re: Calculating Half-life

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.
Tue Feb 14, 2017 12:29 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Textbook Problem #14.27
Replies: 2
Views: 358

Re: Textbook Problem #14.27

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.
Mon Feb 13, 2017 10:15 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Pt in SHE
Replies: 1
Views: 298

Re: Pt in SHE

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.
Tue Feb 07, 2017 12:53 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Platinum
Replies: 1
Views: 259

Re: Platinum

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...
Wed Feb 01, 2017 11:03 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Replies: 1
Views: 262

It means the redox reaction has reached equilibrium.
Mon Jan 23, 2017 1:27 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.19 part a
Replies: 1
Views: 379

Re: 8.19 part a

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 ...
Thu Jan 19, 2017 10:42 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Unit Confusion
Replies: 1
Views: 279

Re: Unit Confusion

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...
Thu Jan 12, 2017 6:00 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Problem 8.49
Replies: 4
Views: 395

Re: Problem 8.49

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.
Tue Nov 29, 2016 6:44 pm
Forum: Identifying Acidic & Basic Salts
Topic: Ions as Bases in CR
Replies: 1
Views: 418

Re: Ions as Bases in CR

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...
Tue Nov 22, 2016 12:22 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Chapter 11 problem 115
Replies: 1
Views: 301

Re: Chapter 11 problem 115

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...
Thu Nov 17, 2016 7:38 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Chemical Equilibrium 11.3
Replies: 1
Views: 319

Re: Chemical Equilibrium 11.3

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.
Thu Nov 10, 2016 1:36 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8252
Views: 1445287

Re: Post All Chemistry Jokes Here

Created by myself while shopping for shampoo.
Tue Nov 01, 2016 5:32 pm
Forum: Empirical & Molecular Formulas
Topic: 2013 Midterm Q2A
Replies: 1
Views: 539

Re: 2013 Midterm Q2A

The method is correct and it will work every time. The "100g" method doesn't REALLY tell you the weight distribution in your sample (how can 8.00 grams of a sample suddenly transform to 100g?), but rather shows you in an easy to comprehend way the distribution of your grams IF you had 100 ...
Mon Oct 24, 2016 10:37 pm
Forum: Lewis Structures
Topic: Lewis Structures Charges Always Balanced?
Replies: 1
Views: 298

Re: Lewis Structures Charges Always Balanced?

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...
Tue Oct 18, 2016 3:59 pm
Forum: Trends in The Periodic Table
Topic: Cation Vs. Anion [ENDORSED]
Replies: 6
Views: 797

Re: Cation Vs. Anion[ENDORSED]

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.
Thu Oct 13, 2016 3:40 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: s and d orbitals
Replies: 3
Views: 558

Re: s and d orbitals

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.
Tue Oct 04, 2016 1:42 am
Forum: Properties of Light
Topic: Textbook Chapter 1, Question 9
Replies: 1
Views: 456

Re: Textbook Chapter 1, Question 9

Use table 1.9 as described on page 6 to determine what wavelength corresponds to what type of wave.
Wed Sep 28, 2016 12:12 am
Forum: SI Units, Unit Conversions
Topic: SI Unit Kg
Replies: 3
Views: 635

Re: SI Unit Kg

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.