Dr. Lavelle,
Thank you so much for putting the amount of work you do into this class. Chemistry Community has provided me with the ability to quickly get my questions answered about difficult concepts. Your passion for chemistry also keeps me interested in class and makes the subject enjoyable.
Search found 19 matches
- Sun Mar 19, 2017 9:43 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Saying Thank You to Dr. Lavelle
- Replies: 490
- Views: 572016
- Tue Mar 07, 2017 8:19 pm
- Forum: *Organic Reaction Mechanisms in General
- Topic: 4.26 ochem textbook
- Replies: 3
- Views: 851
Re: 4.26 ochem textbook
Does the hydrogen have to bond first, or can the steps be written in a different order (i.e. with the Iodine bonding to the carbon structure first.
- Wed Mar 01, 2017 9:20 pm
- Forum: *Organic Reaction Mechanisms in General
- Topic: Activation Energy vs Free energy of activation
- Replies: 3
- Views: 896
Re: Activation Energy vs Free energy of activation
Odel,
The standard Gibbs free energy of activation is always positive because it always takes some free energy to initiate the reaction.
The standard Gibbs free energy of activation is always positive because it always takes some free energy to initiate the reaction.
- Wed Feb 15, 2017 12:30 am
- Forum: Thermodynamic Definitions (isochoric/isometric, isothermal, isobaric)
- Topic: Reversible vs. Irreversible [ENDORSED]
- Replies: 4
- Views: 1102
Re: Reversible vs. Irreversible [ENDORSED]
Two things that whether or not a system is reversible can affect is entropy and work done on the environment. In the case of a reversible process, Delta S system = -Delta S surrondings. This is not the case with an irreversible process.
- Wed Feb 15, 2017 12:20 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Finding Ka
- Replies: 2
- Views: 691
Re: Finding Ka
Ka is the k value of the decomposition of a weak acid (i.e., it is the dissociation constant) it is calculated the same way as K for the rxn. A square root is taken in this equation, because the redox reaction has everything doubled, and the Ka is based on the simplest version of the rxn. We had to ...
- Wed Feb 15, 2017 12:13 am
- Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
- Topic: Winter 2013 Midterm: Question #4
- Replies: 3
- Views: 795
Re: Winter 2013 Midterm: Question #4
Just to clarify, if the pressure changes, but the volume does not, no work is done, right?
- Wed Feb 15, 2017 12:08 am
- Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
- Topic: 2013 Midterm 8B
- Replies: 4
- Views: 999
Re: 2013 Midterm 8B
Angela, both equations work. For whatever reason, they sometimes come out to slightly different numbers, but so long as you show your work and and your calculations are correct you should receive credit. One of the past midterms (either 2016 or 2013, I can't remember) has a situation like this where...
- Tue Feb 14, 2017 9:27 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Midterm 2012 #7
- Replies: 4
- Views: 811
Re: Midterm 2012 #7
You would normally want to make have the equations reduced if you were trying to create a spontaneous rxn (+ E of cell), but it is given with Mn2+ being oxidized so it must be written that way on the final answer.
- Sun Feb 12, 2017 1:38 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: When to add Pt(s) to a cell diagram?
- Replies: 2
- Views: 620
Re: When to add Pt(s) to a cell diagram?
It should be noted that it needs to be a pure, solid (or liquid, in the case of Hg) metal. Metal ions and metals bonded to larger compounds (Ni(OH)2 for example) are not adequately able to conduct electrons.
- Wed Jan 25, 2017 9:46 pm
- Forum: Phase Changes & Related Calculations
- Topic: Calculating Vaporization of water at 85 C
- Replies: 1
- Views: 3500
Calculating Vaporization of water at 85 C
The question is stated as: Calculate the standard entropy of vaporization of water at 85 C, given that its standard entropy of vaporization at 100. C is 109.0 J K 1 mol 1 and the molar heat capacities at constant pressure of liquid water and water vapor are 75.3 J K 1 mol 1 and 33.6 J K 1 mol 1, res...
- Wed Jan 18, 2017 10:49 pm
- Forum: Phase Changes & Related Calculations
- Topic: HW 8.67 [ENDORSED]
- Replies: 5
- Views: 1048
Re: HW 8.67 [ENDORSED]
I have a question regarding b) The question is finding the enthalpy of formation for the liquid state of CH3O3, methanol. According to the solutions manual, you have to add the enthalpy of sublimation for carbon, because carbon is a solid in its ground state. Is there any reason why we use the entha...
- Thu Jan 12, 2017 11:14 am
- Forum: Phase Changes & Related Calculations
- Topic: Systems
- Replies: 2
- Views: 760
Re: Systems
Thanks for the info, very clear and easy to understand.
- Fri Dec 02, 2016 10:48 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Acid strength pattern
- Replies: 3
- Views: 786
Re: Acid strength pattern
From what I understand, it takes bond length/strength do not always have the same effects on acidity. It takes some more complex organic chemistry to explain, having partly to do with the difference between heterolytic and homolytic bond cleavage and the ability of the conjugate base to stabilize th...
- Fri Dec 02, 2016 6:46 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Strength of acids
- Replies: 6
- Views: 1139
Re: Strength of acids
So, higher electron withdrawing ability means a weaker acid? Also, how can one tell what the electron withdrawing ability is of an electron withdrawing group? For example, how would you know that F has a greater electron withdrawing ability than H or CH3? I can see that CH3 would have a lot more ele...
- Fri Dec 02, 2016 6:32 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Acid strength pattern
- Replies: 3
- Views: 786
Re: Acid strength pattern
The logic from the textbook, which says that acid strength depends on polarity, is correct in putting the acidity of the compounds you mentioned as NH3<H2O<HF, with HF being the strongest acid. As far as bond strength, the WEAKER the H-A bond, the STRONGER the acid. To make it more clear, weaker bon...
- Fri Nov 25, 2016 6:53 pm
- Forum: Properties & Structures of Inorganic & Organic Acids
- Topic: Indicators of strong or weak acid/base
- Replies: 3
- Views: 852
Re: Indicators of strong or weak acid/base
Just to clarify, this means that strong acids and bases have no Ka or Kb?
- Sun Nov 13, 2016 5:16 pm
- Forum: Equilibrium Constants & Calculating Concentrations
- Topic: Chem Equilibrium
- Replies: 3
- Views: 700
Re: Chem Equilibrium
By lecture notes does that mean the first 4 pages of the course reader?
- Wed Nov 02, 2016 3:43 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3654365
Re: Post All Chemistry Jokes Here
Q: How many Heisenbergs does it take to change a light bulb?
A: If you know the number, you don't know where the light bulb is.
A: If you know the number, you don't know where the light bulb is.
- Sat Oct 22, 2016 5:24 pm
- Forum: Sigma & Pi Bonds
- Topic: Sigma and Pi Bonds for Quiz 2
- Replies: 3
- Views: 1104
Re: Sigma and Pi Bonds for Quiz 2
Nasir, In short, when carbon bonds with other atoms, the first bond is always a sigma bond, and any subsequent bond is a pi bond. A single bond between, say, carbon and hydrogen would be on sigma bond. A triple bond between, for example, 2 carbon molecules would be made up of one sigma bond and 2 pi...