Search found 36 matches

by Edward_Lee_3C
Sun Mar 19, 2017 12:03 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Pre-Equilibrium
Replies: 2
Views: 360

Re: Pre-Equilibrium

If the k is lower or the activation energy is higher. If it doesn't show you it explicitly maybe count how much bonds were broken/formed in each step. I would assume it would tell you in the problem.
by Edward_Lee_3C
Thu Mar 09, 2017 9:50 pm
Forum: *Organic Reaction Mechanisms in General
Topic: 4.26 ochem textbook
Replies: 3
Views: 558

Re: 4.26 ochem textbook

The Iodine has higher electronegativity so the H would usually bond first.
by Edward_Lee_3C
Tue Mar 07, 2017 6:39 pm
Forum: *Organic Reaction Mechanisms in General
Topic: 4.26 ochem textbook
Replies: 3
Views: 558

Re: 4.26 ochem textbook

Yes it could either one. The only time where you have to put the Iodine on the left or H on the right is when the question shows you the end result and it is like that.
by Edward_Lee_3C
Sat Mar 04, 2017 9:17 pm
Forum: *Alkanes
Topic: Naming
Replies: 2
Views: 334

Re: Naming

It would be more beneficial to focus on IUPAC as you can name any unique molecule you encounter whereas the molecules that have common names are ones that are frequently used.
by Edward_Lee_3C
Thu Mar 02, 2017 11:05 pm
Forum: *Alkanes
Topic: Hydrocarbons memorizations
Replies: 2
Views: 358

Re: Hydrocarbons memorizations

Usually what's in the course reader is what appears on quizzes/tests.
by Edward_Lee_3C
Mon Feb 27, 2017 1:53 pm
Forum: *Nucleophiles
Topic: Nucleophiles and Electronegativity
Replies: 5
Views: 1890

Re: Nucleophiles and Electronegativity

Nucleophiles want to be positive so they want to lose electrons. Because Br- is simply a bigger atom its electrons are held farther way therefore making it easier to remove than F-'s. But electronegativity is "electron pulling power" so that can be applied as well.
by Edward_Lee_3C
Thu Feb 23, 2017 8:43 pm
Forum: General Science Questions
Topic: Homework Problem 4.38d
Replies: 2
Views: 478

Re: Homework Problem 4.38d

In 14A when certain molecules had multiple resonance forms we chose the one that was most stable (ie. central atom had a formal charge equal to 0). Maybe this applies to your question.
by Edward_Lee_3C
Tue Feb 21, 2017 9:22 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: Order of Reactions and its Units
Replies: 1
Views: 381

Re: Order of Reactions and its Units

Rate of reaction is essentially concentration over time, Molarity over time unit (second,minute). In the rate law you are multiplying k by units such as mol/L, s, etc. so the rate constant differs to cancel out units so the rate of reaction ends up as Molarity over time unit
by Edward_Lee_3C
Sun Feb 19, 2017 6:27 pm
Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
Topic: Quiz 2
Replies: 1
Views: 334

Re: Quiz 2

On the thread made by the moderator about Quiz 2, they posted the answers to the quiz 2 preparation but not the work for it.
by Edward_Lee_3C
Sun Feb 12, 2017 5:12 pm
Forum: Balancing Redox Reactions
Topic: Balancing Acids and Bases
Replies: 1
Views: 253

Re: Balancing Acids and Bases

In acidic solution you balance hydrogens by adding H+. In basic solutions you add H2O and add OH- to the other side.
by Edward_Lee_3C
Sat Feb 11, 2017 12:55 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: E knot +/- sign [ENDORSED]
Replies: 1
Views: 299

Re: E knot +/- sign [ENDORSED]

If you plan on calculating the E value by approaching it like a Hess' Law you would change the sign when reversing the equation. If you're using the other way to calculate the Ecell value then you wouldn't change the sign.
by Edward_Lee_3C
Wed Feb 08, 2017 11:26 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: 14.41
Replies: 4
Views: 538

Re: 14.41

For redox reactions you have to balance the H's and O's with H2O,H+,or OH- depending if it is an acidic solution or basic solution. Try it without balancing by changing the coefficient.
by Edward_Lee_3C
Mon Feb 06, 2017 9:21 pm
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.21a - sign of cell potentials
Replies: 1
Views: 258

Re: 14.21a - sign of cell potentials

You're mixing the two ways to calculate the standard E. Dr. Lavelle mentioned in class to only switch signs if you're doing it like a Hess' Law problem. Otherwise keep the sign if you're using the equation.
by Edward_Lee_3C
Fri Feb 03, 2017 12:50 am
Forum: Balancing Redox Reactions
Topic: Balancing for E
Replies: 2
Views: 343

Re: Balancing for E

If you watch the bruincast for wednesday he explains why "we use the positive value of 0.34 instead even though the redox reaction says Copper is losing electrons. Shouldn't it be Ecell=0.77 - (-0.34)=1.11 ? ". We also balance it to cancel out the electrons and balancing our equations will...
by Edward_Lee_3C
Sun Jan 29, 2017 3:25 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies
Replies: 1
Views: 280

Re: Bond Enthalpies

It's just there to give you the value when you need to break solid carbon in graphite form. The values are usually given in the table and when it is not the problem seems to always include what you need.
by Edward_Lee_3C
Fri Jan 27, 2017 3:34 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Reversable
Replies: 2
Views: 356

Re: Reversable

It would usually tell you. If the external pressure changes that is a good indication that it is reversible.
by Edward_Lee_3C
Mon Jan 23, 2017 8:01 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Reversible/Irreversible Pathways
Replies: 1
Views: 336

Re: Reversible/Irreversible Pathways

Today he explained the graphs for the reversible and irreversible processes. For the reversible process, the external pressure is slowly reduced so that is why the line slopes downward. Because the pressure is changing the P* change in V cannot be used. For the irreversible process, the external pre...
by Edward_Lee_3C
Sat Jan 21, 2017 11:10 pm
Forum: Phase Changes & Related Calculations
Topic: Homework [ENDORSED]
Replies: 2
Views: 452

Re: Homework [ENDORSED]

Dr. Lavelle always says he puts atleast one homework question on every test.
by Edward_Lee_3C
Fri Jan 20, 2017 2:14 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Cv vs Cp
Replies: 1
Views: 224

Re: Cv vs Cp

at constant volume vs at constant pressure. Read the question if it says a monatomic and at constant pressure you use the one that corresponds to the conditions.
by Edward_Lee_3C
Mon Jan 16, 2017 2:30 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpies Question 75 B
Replies: 1
Views: 215

Re: Bond Enthalpies Question 75 B

C-H bonds broken on reactants probably equal the same number of C-H bonds in product so it cancels. They probably didn't want to write everything.
by Edward_Lee_3C
Thu Jan 12, 2017 6:17 pm
Forum: Calculating Work of Expansion
Topic: Problem 8.3
Replies: 3
Views: 396

Re: Problem 8.3

keep it in centimeters because cm^3 is equivalent to L
by Edward_Lee_3C
Wed Jan 11, 2017 7:51 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Calculating the Heat Given Off By a Reaction
Replies: 2
Views: 306

Re: Calculating the Heat Given Off By a Reaction

convert the grams to moles if the molecule is given. grams over molar mass to get moles and use the moles as the n.
by Edward_Lee_3C
Wed Nov 30, 2016 10:20 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: Henderson-Hasselbalch pOH
Replies: 1
Views: 388

Re: Henderson-Hasselbalch pOH

It's something like pOH = pKb + log([BH+]/[B]). You can find it online.
by Edward_Lee_3C
Wed Nov 30, 2016 10:18 pm
Forum: *Making Buffers & Calculating Buffer pH (Henderson-Hasselbalch Equation)
Topic: 13.1
Replies: 1
Views: 350

Re: 13.1

It's because the solid sodium acetate dissociates in water creating Na+(aq) and C2H3O2- (aq). If you add more of the solid sodium acetate it means an increase in C2H3O2- (aq).
by Edward_Lee_3C
Mon Nov 28, 2016 1:45 am
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Pressure, Temperature, Etc
Replies: 1
Views: 222

Re: Pressure, Temperature, Etc

When pressure increases the reaction favors the side with less moles or molecules because it wants to reduce the force when the gas molecules hit the sides of the container. For temperature you need to figure out if the reaction is endothermic or exothermic. You can do this by looking at delta H tha...
by Edward_Lee_3C
Sat Nov 19, 2016 5:02 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Which is weaker/stronger?
Replies: 2
Views: 378

Re: Which is weaker/stronger?

If the Ka, acidity constant, is low then that means only a small portion of the acid molecules donate their protons, meaning it incompletely deprotonates which is a clear indication of a weak acid.
by Edward_Lee_3C
Sat Nov 19, 2016 4:14 pm
Forum: Acidity & Basicity Constants and The Conjugate Seesaw
Topic: Which is weaker/stronger?
Replies: 2
Views: 378

Re: Which is weaker/stronger?

Take the negative log of the concentration of hydronium ions in the solution. This is to find the pH of the solution. 1-6 is acidic and the lower the pH the more acidic it gets. He was talking about the molarity of the acids where 1.0*10^-6 M hydronium would be a weaker acid than 1.0*10^-3 M hydronium
by Edward_Lee_3C
Sun Nov 13, 2016 2:11 pm
Forum: Photoelectric Effect
Topic: Midterm question #3A
Replies: 2
Views: 510

Re: Midterm question #3A

The threshold energy they provide is kJ/mol. You need to convert it to just J
by Edward_Lee_3C
Sat Nov 05, 2016 7:07 pm
Forum: Hybridization
Topic: Which Hybrid Orbital
Replies: 6
Views: 708

Re: Which Hybrid Orbital

Count the number of electron densities (where there is bonding/lone pairs) sp = 2 electron densities sp^2 = 3 electron densities sp^3 = 4 electron densities sp^3d = 5 electron densities sp^3d^2 = 6 electron densities The central atom in trigonal planar bonds in three places and has no lone pairs so ...
by Edward_Lee_3C
Fri Oct 28, 2016 8:31 pm
Forum: Administrative Questions and Class Announcements
Topic: Midterm 1
Replies: 2
Views: 445

Re: Midterm 1

everything till the end of hybridization, so not all of chapter four.
by Edward_Lee_3C
Sun Oct 23, 2016 4:48 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Formal Charge
Replies: 1
Views: 274

Re: Formal Charge

The way I count formal charge is every dot is +1 and every bond is +1 to the total. So if there is a double bond I would count 2, one for each bond I see.
by Edward_Lee_3C
Wed Oct 19, 2016 10:42 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: 2.55
Replies: 3
Views: 717

Re: 2.55

The answer for c is (n-1)d^5 ns^2 not (n-1)d^3ns^2. Is the solutions wrong or did the question word c weirdly meaning the fifth group in the transition metals section not the fifth group of the periodic table?
by Edward_Lee_3C
Wed Oct 12, 2016 11:08 pm
Forum: Trends in The Periodic Table
Topic: Chapter 2, Homework Problem 2.45
Replies: 3
Views: 808

Re: Chapter 2, Homework Problem 2.45

Since these are ground-state electron configurations means numbers of electrons = number of protons. Add all the electrons in the ground-state electron configuration and find the same number on the periodic table and you will get the element predicted to have that configuration. For example, [Kr] = ...
by Edward_Lee_3C
Thu Oct 06, 2016 8:36 pm
Forum: Heisenberg Indeterminacy (Uncertainty) Equation
Topic: Question about HW1.45 and how to determine the incertainty of velocity [ENDORSED]
Replies: 1
Views: 355

Re: Question about HW1.45 and how to determine the incertainty of velocity [ENDORSED]

If you check the Solution Manuel Errors on Dr. Lavelle's website 1.45 is on there and you're completely right!
by Edward_Lee_3C
Sat Oct 01, 2016 5:21 pm
Forum: Properties of Electrons
Topic: Atomic Spectra Post Assessment Question
Replies: 3
Views: 605

Re: Atomic Spectra Post Assessment Question

I'm not too sure as well but since 1,650,763.73 wavelengths equals 1 meter. You divide 1 meter by 1,650,763.73 to get 6.06*10^-7. If you check the wavelength chart, it is in the visible light region and to find the energy you can use E=(hc)/wavelength.

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