Search found 25 matches
- Thu Mar 16, 2017 2:06 pm
- Forum: *Haloalkanes
- Topic: Priority when Naming
- Replies: 2
- Views: 1454
Re: Priority when Naming
First functional groups, then double/triple bonds and then substituents. So you're correct. Dr. Lavelle has stated he wouldn't give us 2 functional groups. See the forum below for verification. Check out this long thread for more info: https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=83&t=200...
- Thu Mar 16, 2017 1:54 pm
- Forum: *Cyclopropanes and Cyclobutanes
- Topic: Torisonal vs. Steric Strain
- Replies: 2
- Views: 1510
Re: Torisonal vs. Steric Strain
Torsional Strain: When rotating a molecule around a bond, the torsional strain is the repulsion caused by the electrons in between different groups when they pass by each other. Torsional strain can be lessened by rotating a molecule around a bond. Steric Strain: Strain caused by the electrons in be...
- Sun Mar 12, 2017 6:33 pm
- Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
- Topic: Torsional Strain
- Replies: 1
- Views: 551
Re: Torsional Strain
When a molecule is able to rotate around a sigma bond, there is bound to be different levels of torsional strain that vary with the placements of the substituents relative to each other. This leads to different conformations of molecules (such as staggered or eclipsed) with different energy levels, ...
- Sat Mar 04, 2017 8:52 pm
- Forum: *Free Energy of Activation vs Activation Energy
- Topic: Activation energy [ENDORSED]
- Replies: 1
- Views: 859
Re: Activation energy [ENDORSED]
The minimum energy requirement that must be met for a chemical reaction to occur is called the activation energy, Ea. The activation energy (Ea), labeled ΔG‡ is the energy difference between the reactants and the activated complex, also known as transition state. In a chemical reaction, the transiti...
- Sun Feb 26, 2017 4:39 pm
- Forum: Arrhenius Equation, Activation Energies, Catalysts
- Topic: Relationship between k, T, and Ea Graph
- Replies: 1
- Views: 546
Re: Relationship between k, T, and Ea Graph
The y-axis is the fraction of molecules, so if the peak of the high temperature curve is lower that means that there are less molecules at that certain level of kinetic energy. As the graph shows, the further right you go on the x-axis, the greater the kinetic energy. I assume that fraction of molec...
- Sat Feb 18, 2017 7:31 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: Cell Diagrams [ENDORSED]
- Replies: 3
- Views: 707
Re: Cell Diagrams [ENDORSED]
If you have non metal/ion pair undergoes redox, most of the time you need solid electrode to supply e-. These electrodes can be on either ends of the cell diagram.
- Sun Feb 12, 2017 8:39 pm
- Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
- Topic: When to add H+ in cell diagram?
- Replies: 1
- Views: 561
Re: When to add H+ in cell diagram?
This forum post may answer your question: https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=140&t=5207&sid=8a327eb0369821b49facabd48e3cc546
- Sun Feb 12, 2017 8:37 pm
- Forum: Entropy Changes Due to Changes in Volume and Temperature
- Topic: Comparing molar entropies of different molecules
- Replies: 1
- Views: 715
Re: Comparing molar entropies of different molecules
A question like this was asked in our last quiz. Basically what it comes down to is: Number of atoms/Number of unique positions of the atoms (degeneracy) Rigidity of bonds For example, which has larger molar entropy, CO or N 2 ? t=0K, and both molecules have the same geometry. Since the number of at...
- Sat Feb 04, 2017 1:03 pm
- Forum: Interesting Applications: Rechargeable Batteries (Cell Phones, Notebooks, Cars), Fuel Cells (Space Shuttle), Photovoltaic Cells (Solar Panels), Electrolysis, Rust
- Topic: H2O->H+ + OH-
- Replies: 2
- Views: 8734
Re: H2O->H+ + OH-
This was a response by Chemmod a couple of years ago: This reaction is the opposite of Problem 13.11d so to make the comparison easier I will flip this reaction (this does not change the chemistry). In that problem you are given the cell diagram to help in the selection and you then solve for the f...
- Sat Jan 28, 2017 8:59 pm
- Forum: General Science Questions
- Topic: Sig Figs
- Replies: 5
- Views: 1112
Re: Sig Figs
Prof Lavelle typically requires us to round at the end of a calculation.
- Sat Jan 28, 2017 8:54 pm
- Forum: Van't Hoff Equation
- Topic: Van't hoff equation
- Replies: 1
- Views: 719
Re: Van't hoff equation
The Van't Hoff Equation allows us to see how temperature changes can affect K. Here is a breakdown of the components of the equation: K 1 = initial equilibrium constant K 2 = final equilibrium constant \Delta H ^{_{\circ }} = standard formation of enthalpy R= Gas constant T 1 = initial temperature T...
- Sun Jan 22, 2017 10:36 pm
- Forum: Concepts & Calculations Using First Law of Thermodynamics
- Topic: open system
- Replies: 2
- Views: 779
Re: open system
I like to think of these problems like they have a moveable piston; one that moves up or down while responding to volume changes inside the beaker/cylinder in order to make the internal and external pressure equal, as it is in a open system. For example, Gas A (3 L) and Gas B (2 L) react to form 6 L...
- Sun Jan 22, 2017 10:09 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Exam Formula Sheet
- Replies: 2
- Views: 724
Re: Exam Formula Sheet
The equations on the back-side of the laminated periodic table you received with your course reader are all the possible equations and constants Prof Lavelle will supply us during an exam. In Chem14A, he picked the formulas that were relevant to us as the time and attached them to the test; I'm assu...
- Sun Jan 15, 2017 5:56 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Username
- Replies: 2
- Views: 835
Re: Username
1. Login 2. On the top right hand of your screen, click on your current username . (it has a upside-down triangle next to it; this will open three more options in a drop down box) 3. Click on User Control Panel 4. Under edit account settings , change your username 5. Enter your current password in t...
- Sun Jan 15, 2017 5:51 pm
- Forum: Phase Changes & Related Calculations
- Topic: CLOSED vs ISOLATED
- Replies: 3
- Views: 814
Re: CLOSED vs ISOLATED
In a open system, the system is not sealed and is not insulated . In a closed system, the system is sealed but is not insulated . In a isolated system, the system is sealed and insulated . When a system is sealed, matter cannot be exchanged with its surrounding; when it's not sealed it can. When a s...
- Wed Nov 30, 2016 5:07 pm
- Forum: Administrative Questions and Class Announcements
- Topic: Chemical Equilibria
- Replies: 1
- Views: 520
Re: Chemical Equilibria
I'm assuming yes because in the course reader it is outlined how to convert between Partial Pressure (Kp) and Concentration (K). See page 133.
- Sun Nov 27, 2016 9:53 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3589565
Re: Post All Chemistry Jokes Here
An atom loses an electron.
It says, "Man, I really have to keep a better ion them!"
It says, "Man, I really have to keep a better ion them!"
- Sun Nov 27, 2016 9:39 pm
- Forum: Identifying Acidic & Basic Salts
- Topic: Identifying a salt
- Replies: 4
- Views: 1256
Re: Identifying a salt
Taken from http://study.com/academy/lesson/what-is-salt-in-chemistry-definition-formula.html because they have a clear, concise definition: In chemistry, a salt is an ionic compound which is made up of two groups of oppositely charged ions. The ion with a positive charge is called a cation, and the ...
- Sat Nov 12, 2016 1:42 pm
- Forum: Naming
- Topic: Oxidation Numbers
- Replies: 1
- Views: 576
Re: Oxidation Numbers
You determine the charges on all the ligands/atoms. If the molecule is neutral (which coordination compounds by their very definition are), then the charges must equal zero; therefore, the oxidization number of the central atom will equal whatever charge makes the molecule neutral. Here is a very si...
- Wed Nov 02, 2016 2:56 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Square Pyramidal
- Replies: 2
- Views: 1175
Re: Square Pyramidal
These (credible) websites suggest that it's 90/120 degree angles. http://chem.libretexts.org/Core/Inorganic_Chemistry/Molecular_Geometry/Square_Pyramidal http://butane.chem.uiuc.edu/pshapley/GenChem2/A1/3.html http://homepage.smc.edu/scholefield_michelle/chem11/handouts/VSEPR%20Theory%20and%20the%20...
- Sun Oct 30, 2016 9:36 pm
- Forum: Dipole Moments
- Topic: Dipole Moments And Polarity
- Replies: 1
- Views: 1140
Re: Dipole Moments And Polarity
Dipole moments can cancel if the molecule is symmetrical. Example: BeF 2 . The charges are vectors so if they go in opposite directions and have the same charge, (when you add them) they will cancel. You don't really need to have knowledge of vectors, just know if it's going in opposite directions a...
- Sun Oct 23, 2016 6:59 pm
- Forum: Determining Molecular Shape (VSEPR)
- Topic: Sigma and Pi Bonds
- Replies: 2
- Views: 697
Re: Sigma and Pi Bonds
We will not be tested on Sigma and Pi bonds in quiz #2. Only material from chapter 2-3.
- Sun Oct 23, 2016 6:54 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3589565
Re: Post All Chemistry Jokes Here
Why did carbon marry hydrogen?
They bonded really well from the moment they met.
They bonded really well from the moment they met.
- Sun Oct 16, 2016 10:10 pm
- Forum: Student Social/Study Group
- Topic: Post All Chemistry Jokes Here
- Replies: 9651
- Views: 3589565
Re: Post All Chemistry Jokes Here
Here's another one from chemistry cat:
- Fri Oct 07, 2016 2:42 pm
- Forum: Wave Functions and s-, p-, d-, f- Orbitals
- Topic: Orbital Question [ENDORSED]
- Replies: 3
- Views: 846
Orbital Question [ENDORSED]
Is it still accurate/appropriate to write (for example, carbon) 1s2 2s2 2p2 instead of what we learned today: 1s2 2s2 2px1 2py1 ?