Search found 20 matches

by Natalie Rotstein 3J
Sun Mar 19, 2017 1:26 pm
Forum: Balancing Redox Reactions
Topic: Help on problem 14.17
Replies: 4
Views: 507

Re: Help on problem 14.17

How do we know that the permanganate becomes a manganese ion and doesn't just lose electrons to the iron?
by Natalie Rotstein 3J
Sun Mar 19, 2017 1:13 pm
Forum: *Organic Reaction Mechanisms in General
Topic: The types of reactions
Replies: 1
Views: 312

Re: The types of reactions

The main types of reactions (I'm assuming you're referring to the electrophilic/nucleophilic rxns), are: -electrophilic addition, where an electrophile is added to another molecule. -bimolecular nucleophilic substitution (Sn2) in which one nucleophile replaces another nucleophile. This often looks l...
by Natalie Rotstein 3J
Sun Mar 19, 2017 12:16 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 2013 Final #3
Replies: 1
Views: 206

2013 Final #3

For the 2013 final, on question 3, were the cell potentials of the half reactions given, or are they supposed to be determined somehow? On the answer key it looks as if the cell potentials are a part of the answer to part A, but how would that be found?
by Natalie Rotstein 3J
Thu Mar 09, 2017 11:36 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz 3 Winter 2017
Replies: 183
Views: 14688

Re: Quiz 3 Winter 2017

Thank you for clarifying, I was mainly confused about whether we would need to know alkene structures/formulas from the name for alkenes other than the ones mentioned in lecture in the context of the electrophilic addition, such as ethene and 2-butene, but I think I understand what we need to know n...
by Natalie Rotstein 3J
Thu Mar 09, 2017 11:16 pm
Forum: *Alkanes
Topic: Naming Help
Replies: 7
Views: 599

Re: Naming Help

Generally alphabetical order is just for the ordering of the name, not the numbering, but I think it might be good form to start with the 1 with the first named substitutent in the previously described situation where every single carbon had a substitutent attached.
by Natalie Rotstein 3J
Thu Mar 09, 2017 11:13 pm
Forum: *Free Energy of Activation vs Activation Energy
Topic: Delta G Double Dagger 2 vs Ea2
Replies: 2
Views: 737

Re: Delta G Double Dagger 2 vs Ea2

ΔG double dagger can be between intermediate and transition or reactant and transition. It is usually shown as reactant to transition though. I think the difference isn't where in the graph it is measured but more just the context - they seem to be equivalent if you look at the equations to calculat...
by Natalie Rotstein 3J
Thu Mar 09, 2017 10:36 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz 3 Winter 2017
Replies: 183
Views: 14688

Re: Quiz 3 Winter 2017

The quiz 3 prep includes alkenes and cycloalkenes, and Lavelle's responses to questions on the quiz prep problems seem to imply that we are expected to know how to solve all of the problems in the quiz prep, but the beginning of the thread it says alkanes and cycloalkanes in the textbook and only up...
by Natalie Rotstein 3J
Wed Feb 22, 2017 12:23 am
Forum: General Rate Laws
Topic: Units of K
Replies: 1
Views: 198

Re: Units of K

It's positive for the thing being considered; for the equation you mentioned, the reason one side is negative is because the concentration of the reactants decreases while the concentration of the products increases, making the change in reactants negative and products positive. To counter this so t...
by Natalie Rotstein 3J
Tue Feb 21, 2017 11:25 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Rate Determining Step
Replies: 3
Views: 356

Re: Rate Determining Step

If a step is "very very slow," and that is the slowest specification for the rate of any step, it is the rate determining step. Because that step determines rate, a faster step prior to it would not affect the rate of the reaction, and therefore would not be included in the rate expression.
by Natalie Rotstein 3J
Tue Feb 21, 2017 11:20 pm
Forum: Second Order Reactions
Topic: Orders for Reactions
Replies: 2
Views: 271

Re: Orders for Reactions

In the textbook, it is said that "the rate law for a reaction is determined experimentally and cannot in general be inferred from the chemical equation for the reaction." I think that in general, the order might look like it can be "found" with the coefficients, but in reality th...
by Natalie Rotstein 3J
Tue Feb 21, 2017 10:34 pm
Forum: Zero Order Reactions
Topic: 15.99
Replies: 2
Views: 386

Re: 15.99

For 0 order reactions, t1/2=[A]0/2k, which means t1/2 is proportional to A, which corresponds to a linear graph. For second order, however, t1/2=1/(k[A]0), which means t1/2 is proportional to 1/A - the graph of 1/x is not linear, so therefore the second order half life graph would also be nonlinear
by Natalie Rotstein 3J
Thu Feb 02, 2017 10:02 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: HW Problem 9.13 - Number of Moles
Replies: 1
Views: 264

HW Problem 9.13 - Number of Moles

I was working on problem 9.13, and I initially was going to use the equations ∆S=nRln(T2/T1) and ∆S=nRln(V2/V1), because they seemed appropriate, but I ended up stuck because they did not give the number of moles, and I didn't see any way to calculate it. I then went to the answer manual to figure o...
by Natalie Rotstein 3J
Sat Dec 03, 2016 5:47 pm
Forum: Identifying Acidic & Basic Salts
Topic: 12.65 (e) and (f)
Replies: 4
Views: 855

Re: 12.65 (e) and (f)

I was wondering this as well, and also, if which metal ions form water complexes and how they do it is something we would need to know for the final or if that information would be given to us if there was a question about it?
by Natalie Rotstein 3J
Fri Dec 02, 2016 12:14 am
Forum: Student Social/Study Group
Topic: Fall 2013 Q2C
Replies: 1
Views: 732

Re: Fall 2013 Q2C

All of the other ones have 10 electrons combined after the [kr] configuration - those electrons could theoretically leave the 5s shell and go to fill the 4d shell instead (that's how Pd can be 4d10). In+, however, has a combined total of 12 electrons after the [kr] configuration, so the configuratio...
by Natalie Rotstein 3J
Fri Dec 02, 2016 12:02 am
Forum: Octet Exceptions
Topic: 2013 Final 4 C
Replies: 1
Views: 367

Re: 2013 Final 4 C

IF5 is polar because of the electron pair on the central atom. Because of this pair, the electron geometry would be octahedral. If you think of the electronegativity of each atom as a sort of "pull," there is one Fluorine that has an electron pair opposite it in the molecules structure, in...
by Natalie Rotstein 3J
Sun Nov 20, 2016 5:42 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Percent Decomposition
Replies: 1
Views: 3364

Re: Percent Decomposition

To get percent decomposition, you need to find the initial amount of the reactant, and then the final amount of the reactant. Then, subtract the final from the initial, and that is the amount that decomposed. Then, divide that number by the initial number, and that should give you the percent decomp...
by Natalie Rotstein 3J
Sun Nov 20, 2016 5:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equilibrium constant help
Replies: 1
Views: 195

Re: Equilibrium constant help

The calculation of the equilibrium constant does exclude liquid and solid concentrations. Though Kc and Kp are both forms of the equilibrium constant, Kc is when calculating it from molarity (for aqueuous solitions and gases), while Kp is when calculating from partial pressure (generally used more f...
by Natalie Rotstein 3J
Sun Oct 30, 2016 9:00 pm
Forum: Empirical & Molecular Formulas
Topic: Mass % Composition
Replies: 3
Views: 477

Re: Mass % Composition

I doubt we would need to when we can just do it the way you said. Generally, I think the % mass composition would be the information given if in a problem where we need to find the empirical formula as opposed to chemical formula, because empirical is just ratios of atoms as opposed to the actual nu...
by Natalie Rotstein 3J
Wed Oct 12, 2016 5:28 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7337
Views: 802006

Re: Post All Chemistry Jokes Here

Thought this one was worth sharing Image
by Natalie Rotstein 3J
Sun Oct 02, 2016 10:30 pm
Forum: General Science Questions
Topic: Rusty on High School Chem [ENDORSED]
Replies: 113
Views: 34711

Re: Rusty on High School Chem [ENDORSED]

I've found that Sparknotes actually has really helpful reviews of high school / AP chemistry topics; they aren't super detailed but if you mainly need just a refresher on what you learned previously, they're a good resource. I've used them in the past to review for AP exams for various subjects.

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