Search found 21 matches

Wed Mar 15, 2017 10:49 pm
Forum: Administrative Questions and Class Announcements
Topic: Saying Thank You to Dr. Lavelle
Replies: 291
Views: 136167

Re: Saying Thank You to Dr. Lavelle

Dr. Lavelle, Although I still can't say chemistry is my favorite subject, I really think having you as a teacher really challenged me to think analytically and problem solve. I appreciate the positive attitude you project in lectures and how you provide all these resources for your students. It has ...
Tue Mar 07, 2017 9:44 pm
Forum: *Alkanes
Topic: Drawing/Labeling reaction profile
Replies: 3
Views: 468

Re: Drawing/Labeling reaction profile

My TA told me that the class would focus more on exergonic reactions. So when they tell us to draw the reaction profiles, they would also tell us if the reaction was exergonic or endergonic. If it's exergonic, the reactants start off higher than the products, and if endergonic vice versa.
Tue Mar 07, 2017 9:33 pm
Forum: *Alkanes
Topic: Alkane name
Replies: 3
Views: 457

Re: Alkane name

I think if you're having trouble identifying the parent chain, you can just count all the C's outside the parentheses, then consider the one in parentheses the subsituent of the adjacent C atom.
Wed Mar 01, 2017 11:03 pm
Topic: Electrophilic addition reaction of HBr and Propene
Replies: 2
Views: 431

Re: Electrophilic addition reaction of HBr and Propene

I was also thinking the same thing: whether it can be written as CH3-CHBr-CH3 as opposed to CH3-CH2-CH2Br.
Wed Feb 22, 2017 3:55 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Quiz 2 Practice Question 11
Replies: 2
Views: 362

Re: Quiz 2 Practice Question 11

I think we might have to use the first order equation: ln(k2/k1)=Ea/R * ((1/T1)-(1/T2)). Maybe first solving for Ea, then using the equation again to solve for k2 at 770 K.
Tue Feb 14, 2017 4:24 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: .05916 In Nernst Equation
Replies: 5
Views: 828

Re: .05916 In Nernst Equation

I think the answer should be the same even if you used the one with 'ln' instead of 'log'. But then instead, it would be 0.02568/n when you plug it into the Nernst equation: {Ecell= Escp - (0.02568/n)*lnQ}
Tue Feb 07, 2017 5:34 pm
Forum: Calculating Work of Expansion
Topic: Entropy - Reversible vs Irreversible
Replies: 3
Views: 546

Re: Entropy - Reversible vs Irreversible

I think it may have something to do with entropy being a state function. So if the reaction returns to the same state it was in before, then there was no change.
Wed Feb 01, 2017 9:08 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Bond Enthalpies
Replies: 7
Views: 690

Re: Bond Enthalpies

Also, I think it would require more energy to break the double bond than it would be to break the single bond (if you want to say something in terms of energy).
Wed Jan 25, 2017 7:41 pm
Forum: Phase Changes & Related Calculations
Topic: Derivations
Replies: 21
Views: 2487

Re: Derivations

I think most of what will be asked for is the manipulation of given equations to solve for problems.
For example, delta U= q+w; since w=-PV we can substitute it into the equation -> delta U= q - PV
Wed Jan 18, 2017 2:43 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Enthalpy [ENDORSED]
Replies: 3
Views: 489

Re: Enthalpy[ENDORSED]

Since a bond is being formed, energy is being released from the system and the enthalpy of that part of the system would be negative.
In the case where a bond is being broken, energy is being taken up by the system to break a bond and the enthalpy of that part of the system would be positive.
Fri Jan 13, 2017 4:58 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calculating the Heat Given Off By a Reaction
Replies: 2
Views: 317

Re: Calculating the Heat Given Off By a Reaction

I think you can use the equation [q= m* Csp *(delta T)], where m is mass in grams, to find the "specific heat capacity".
Sat Dec 03, 2016 1:49 pm
Forum: Dipole Moments
Topic: Dipole and Polarity [ENDORSED]
Replies: 3
Views: 592

Re: Dipole and Polarity[ENDORSED]

If given a list of molecules, how would you determine which has the highest dipole moment? (Assuming they all have dipole moments)
Tue Nov 22, 2016 6:53 pm
Forum: Lewis Acids & Bases
Topic: strong or weak acid
Replies: 6
Views: 947

Re: strong or weak acid

The longer the bond, the stronger the acid; for example this order from weakest to strongest acids:
H-F < H-Cl < H-Br < H-I
Wed Nov 16, 2016 11:48 am
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Identifying Polydentates? [ENDORSED]
Replies: 8
Views: 1258

Re: Identifying Polydentates?[ENDORSED]

Is there a way to identify whether something is mono-, bi-, try-, etc. dentate just by looking at the compound given? Or do we always have to draw the structure?
Sat Nov 12, 2016 4:08 pm
Forum: Shape, Structure, Coordination Number, Ligands
Topic: Shape of coordination compound
Replies: 3
Views: 846

Re: Shape of coordination compound

I think we should know the structure of the coordination compound if we were asked about the dentisity of the compound (eg. the polydentate: EDTA)
Tue Nov 01, 2016 9:27 am
Forum: Ionic & Covalent Bonds
Topic: Covalent and Ionic Character
Replies: 3
Views: 799

Re: Covalent and Ionic Character

So is there a quick way to determine the order of ionic/covalent characteristics just by looking at the periodic table? The closer two elements are to each other in a molecule on the periodic table, the more covalent they are. The farther they are from each other on the periodic table, the more ioni...
Wed Oct 26, 2016 11:06 pm
Forum: Lewis Structures
Topic: Noble Gas as central atom
Replies: 1
Views: 562

Noble Gas as central atom

Since Xenon can be considered a central atom, does that mean Krypton and Radon can also act as the central atom?
Mon Oct 17, 2016 6:27 pm
Forum: Lewis Structures
Topic: Chapter 3 #57 [ENDORSED]
Replies: 2
Views: 362

Re: Chapter 3 #57[ENDORSED]

The central atom should be the one with the least electronegativity. From left to right on the periodic table, electronegativity increases. From top to bottom, electronegativity decreases. So for a) sulfite ion, the sulfur ion would be in the middle and connected to 3 oxygens. Even though they are i...
Mon Oct 10, 2016 10:45 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Showing Work [ENDORSED]
Replies: 3
Views: 573

Re: Showing Work[ENDORSED]

Plus, in my opinion, showing work helps make sure you're on the right track, like having the correct units for your numbers and also having the right amount of sig figs in the end.
Wed Oct 05, 2016 9:36 am
Forum: DeBroglie Equation
Topic: Worked Example on page 52 in the Course Reader
Replies: 2
Views: 417

Re: Worked Example on page 52 in the Course Reader

Yeah. I think Professor Lavelle just meant 10^15 was the general cutoff point to determine if a wavelength is measurable. Like if a question were to ask whether an object with a certain mass and velocity has a measurable wavelength, 10^15 would be the cutoff. >10^15 meaning it is, and <10^15 meaning...
Mon Sep 26, 2016 4:47 pm
Forum: Empirical & Molecular Formulas
Topic: Calculating Molecular and Empirica Formulas
Replies: 5
Views: 1371

Re: Calculating Molecular and Empirica Formulas

This is an example we did in our discussion session, if you find it helpful. Ex. Caffeine is 49.48% C, 5.19% H, 16.4% O, and 28.61% N. Find the empirical formula. 1. First, we had to assume it was over 100 g so that we could get rid of the percentages and make them into grams. 2. Then we divide each...