## Search found 22 matches

Fri Mar 17, 2017 3:31 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Simplified Nernst equation
Replies: 1
Views: 358

### Re: Simplified Nernst equation

R(8.314) times T(298) divided by F (96485.3) should give you 0.02567823285, which is slightly off from what the answer key says, but should be acceptable for the following calculations. I believe on some of the equation sheets we were given with our course readers Faraday's constant looks like 96485...
Mon Mar 06, 2017 11:08 pm
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalyst [ENDORSED]
Replies: 2
Views: 285

### Re: Catalyst[ENDORSED]

Even if isn't present in the overall reaction, if the catalyst is present in the rate limiting step, it should still be included in the rate of reaction equation. Remember though that catalysts don't change the reaction's equilibrium so they aren't included in calculations for the equilibrium consta...
Mon Feb 27, 2017 10:52 pm
Forum: *Alkanes
Topic: Equivalent numbering - meaning?
Replies: 2
Views: 320

### Re: Equivalent numbering - meaning?

I think the phrasing is referring to the fact that if you started numbering at the other end the methyl substituent would be at position 3 and the ethyl substituent at 5, so there are 2 constituents both at the 3 or 5 position either way you start from (making them "equivalent"). The examp...
Wed Feb 22, 2017 9:08 pm
Forum: First Order Reactions
Topic: integral
Replies: 1
Views: 310

### Re: integral

\frac{d[A]}{[A]} can be manipulated to \int \frac{1}{[A]} d[A] , and after integrating that you would get \ln [A] , which is a standard integral I think we're just supposed to memorize. There are different rules for finding derivatives, but I don't think we have to know them very well for this sect...
Mon Feb 20, 2017 12:10 am
Forum: Kinetics vs. Thermodynamics Controlling a Reaction
Topic: Interpreting graphs [ENDORSED]
Replies: 3
Views: 388

### Re: Interpreting graphs[ENDORSED]

https://i.stack.imgur.com/yo3Y0.png In a graph like this, subtract the energy of the reactants from the energy of the products. Depending on the sign of the difference in energy, you can tell if it's exothermic or endothermic. Negative means exothermic, and positive indicates an endothermic reactio...
Sun Feb 12, 2017 8:10 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: 9.59
Replies: 1
Views: 244

### Re: 9.59

Make sure you check your negative/positive signs and just make there's a 1.5 coefficient in front of the O2 on the reactants side! That's what tripped me up.
Hope this helped :)
Sun Feb 12, 2017 8:05 pm
Forum: Balancing Redox Reactions
Topic: Oxidation Numbers
Replies: 1
Views: 197

### Re: Oxidation Numbers

Hi! These are some rules that I remember/that I've seen: 1. Uncombined/free elements have an oxidation number of 0. 2. The sum of oxidation numbers in a neutral substance is 0. (Ex. in H 2 O, you know it's neutral so H must be +1 and O is -2) 3. For ions, the sum of oxidation numbers equals the char...
Thu Feb 02, 2017 3:28 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Writing Balanced Equations
Replies: 1
Views: 233

### Re: Writing Balanced Equations

Hi,
Either way it shouldn't matter, because I believe Gibbs free energy is measured in J/mol, so as long as you end up solving for the value per 1 mol, you should be fine.

Hope this helped!
Sat Jan 28, 2017 8:36 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7437
Views: 983591

### Re: Post All Chemistry Jokes Here

First law of thermodynamics? Don't talk about thermodynamics.
Sat Jan 21, 2017 6:54 pm
Forum: Phase Changes & Related Calculations
Topic: Enthalpy of Fusion
Replies: 1
Views: 218

### Re: Enthalpy of Fusion

Hi,
Although it does seem a bit counterintuitive and confusing to name that process "fusion" when nothing is being fused together, the word originates from the Latin fundere, meaning "to melt." It's just a convention that chemists kept!
Mon Jan 09, 2017 8:30 pm
Forum: Phase Changes & Related Calculations
Topic: Understanding why enthalpy is a state function
Replies: 4
Views: 1523

### Re: Understanding why enthalpy is a state function

Hi, Enthalpy is considered a state function because its current value will only depend upon the final and initial values of heat in a reaction, but not the path or process that occurred for it to reach that value. In other words, theoretically a reaction could have the same enthalpy value whether it...
Sun Nov 27, 2016 1:55 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Molecular orbital theory of diatomic molecules
Replies: 1
Views: 352

### Re: Molecular orbital theory of diatomic molecules

Since CO is a heteronuclear molecule you would use the z<8 diagram. Orient the O in a lower position however, since it is more electronegative. Following the diagram, the bonding sigma 2p orbital should be above the bonding pi 2p orbital. It should end up looking like this: http://www.meta-synthesis...
Sun Nov 20, 2016 3:29 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Bonding vs Antibonding
Replies: 1
Views: 238

### Re: Bonding vs Antibonding

To my understanding, it's not the electron itself that is considered weaker, but an electron in an antibonding orbital will result in a weaker bond between two atoms because it has nodes in the bonding region between the nuclei, outside the bonding region. This pulls one nucleus away from the other ...
Fri Nov 11, 2016 11:09 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: When making an M.O. diagram of 2 elements, where one has z<8 and the other one has z>/=8 how do you know which diagram t
Replies: 2
Views: 221

### Re: When making an M.O. diagram of 2 elements, where one has z<8 and the other one has z>/=8 how do you know which diagr

To my understanding, with heteronuclear molecules with 1 atom being z>8 and the other z<8, you should be using the z<8 diagram. Page 111 of the course reader references this!
Fri Nov 11, 2016 11:05 pm
Forum: Administrative Questions and Class Announcements
Topic: Lavelles's email
Replies: 2
Views: 465

### Re: Lavelles's email

It should be lavelle@chem.ucla.edu!
Sun Nov 06, 2016 1:38 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7437
Views: 983591

### Re: Post All Chemistry Jokes Here

What did the orbital think of the chemistry homework?
He thought it was easy pz!
Sat Oct 29, 2016 3:21 pm
Forum: Ionic & Covalent Bonds
Topic: Ionic Character
Replies: 1
Views: 236

### Re: Ionic Character

The term ionic character is used when a large electronegativity difference exists between two atoms, in a way that one atom can possess most of the electrons and seem like an anion while the other resembles a cation. This can happen even if the bond is technically covalent, because in covalent bonds...
Wed Oct 19, 2016 10:46 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2.55
Replies: 3
Views: 597

### Re: 2.55

I interpreted it as the 5th group in the periodic table (V, Nb, Ta, Db) that happen to be transition metals, but if the solutions manual says that, then I guess we were meant to interpret it as the 5th group in the transition metals section. My answer for c would change then.
Wed Oct 19, 2016 10:38 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2.55
Replies: 3
Views: 597

### Re: 2.55

Hi Daniel, (a) The alkali metals are all the metals in Group 1A. They also all belong in the s-block, and will have 1 valence electron each. Therefore, depending on which shell the element is in, the configuration will be ns 1 . For example, sodium's will be 3s 1 . (b) Group 15 elements are in the p...
Sun Oct 16, 2016 8:18 pm
Forum: Resonance Structures
Topic: Electrons in Resonance [ENDORSED]
Replies: 4
Views: 444

### Re: Electrons in Resonance[ENDORSED]

Hi Katie, To add onto what Shirley said, electrons in a resonance structure are considered to be "delocalized." Basically what that means is that they're not considered to be associated with any one atom or bond, and are in a "state of somewhere in between." This electron and cha...
Sun Oct 09, 2016 10:35 pm
Forum: SI Units, Unit Conversions
Topic: Quiz 1
Replies: 1
Views: 280

### Re: Quiz 1

Yeah! What'd you need help with?
Sun Oct 02, 2016 6:13 pm
Forum: Student Social/Study Group
Topic: Dykstra Hall Study Group (Fall 2016)
Replies: 25
Views: 1732

### Re: Dykstra Hall Study Group (Fall 2016)

This seems like such a great idea! Whenever we decide a date or time I'll be there; my email is catherinele98@g.ucla.edu. Hope to see everyone soon!