Search found 30 matches

by Rachel Colbath 2G
Sun Mar 13, 2016 8:05 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Winter 2013 Final Question 3A
Replies: 3
Views: 484

Re: Winter 2013 Final Question 3A

Yes the Half reaction values are given to us. They solved it in 2 ways in that problem. If you are using the formula Cathode - Anode you just plug the positive values (reductions) that you are given on the sheet directly into that formula without changing the sign because the negative in the formula...
by Rachel Colbath 2G
Sun Mar 13, 2016 7:44 am
Forum: Balancing Redox Reactions
Topic: Cell Diagrams
Replies: 4
Views: 611

Re: Cell Diagrams

The Pt(s) are going to be acting as anodes or cathodes that don't affect the solutes and concentrations, they will be placed on either side of the cell diagram as demonstrated above.
by Rachel Colbath 2G
Sun Mar 13, 2016 7:24 am
Forum: Calculating Standard Reaction Entropies (e.g. , Using Standard Molar Entropies)
Topic: Winter 2011 Final Question
Replies: 2
Views: 435

Re: Winter 2011 Final Question

In addition to the Boltzmann equation, you can think about the 2 molecules stacking into a crystal N-0 can stack like this: N-ON-O N-OO-N N-ON-O or it can mix O-NN-O this possibility for mixing contributes to residual entropy at Ok N-ON-O N-ON-O Whereas BF3 doesn't have different possible stackings ...
by Rachel Colbath 2G
Sat Mar 12, 2016 7:39 pm
Forum: *Alkanes
Topic: Priority naming - Alphabetical vs. # substituents
Replies: 1
Views: 301

Priority naming - Alphabetical vs. # substituents

If you have, ex. 3 methyl groups and one chlorine, would you apply the lower number to the trimethyl since there are more of them or the chloro because it comes first alphabetically?

ex. 4-chloro-2,2,4-trimethylpentane
or 2-chloro-2,4,4-trimethylpentane

Thanks!
by Rachel Colbath 2G
Fri Mar 11, 2016 2:51 pm
Forum: *Alkanes and Substituted Alkanes (Staggered, Eclipsed, Gauche, Anti, Newman Projections)
Topic: Winter 2014 final question 7 part F newman projections
Replies: 3
Views: 680

Re: Winter 2014 final question 7 part F newman projections

How would we know that the chlorine is bigger than the methyl group when arranging the second most stable conformation?
by Rachel Colbath 2G
Sun Mar 06, 2016 7:05 pm
Forum: *Alkanes
Topic: Vinyl and allyl groups
Replies: 1
Views: 435

Vinyl and allyl groups

Will vinyl groups ever be used in IUPAC naming or are they just used to distinguish a particular halogen? What is the effect of their distance from the double bond? Does this significantly alter a halogen's effect on the molecule if it is allyl vs. vinyl?
by Rachel Colbath 2G
Sun Feb 28, 2016 10:55 pm
Forum: *Complex Reaction Coordinate Diagrams
Topic: Reaction Profile Delta G
Replies: 4
Views: 1199

Reaction Profile Delta G

In a 2 step reaction, the reaction profile would have two transition states. In the process of figuring out which has a larger delta G, would you measure the difference between the top of both the first and the second transition states to the initial reaction delta G value? Or would you compare TS1 ...
by Rachel Colbath 2G
Fri Feb 19, 2016 9:15 pm
Forum: Method of Initial Rates (To Determine n and k)
Topic: M Calculations
Replies: 1
Views: 403

Re: M Calculations

If you are given a reaction: aA + bB = cC you can use this formula to compare them: -\frac{1}{a}\frac{d[A]}{dt}=-\frac{1}{b}\frac{d[B]}{dt}=\frac{1}{c}\frac{d[C]}{dt} The first two are negative because they are reactants, they are decreasing to form the positive product. If the coefficient of a is o...
by Rachel Colbath 2G
Tue Feb 09, 2016 9:47 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Winter 2015 Midterm Q1 heat
Replies: 1
Views: 359

Re: Winter 2015 Midterm Q1 heat

Water is liquid at 22 degrees as well as 25 degrees, it uses the same heat capacity from 0-100 degrees, you do not need to split this portion into steps.
by Rachel Colbath 2G
Tue Feb 09, 2016 9:19 pm
Forum: Phase Changes & Related Calculations
Topic: Intensive/Extensive
Replies: 5
Views: 952

Re: Intensive/Extensive

is an example of an intensive property
, are examples of extensive properties because they change with the size of the sample.
by Rachel Colbath 2G
Tue Feb 09, 2016 9:07 pm
Forum: Phase Changes & Related Calculations
Topic: Thursday Quiz 1, Question 3; See post for question
Replies: 3
Views: 462

Re: Thursday Quiz 1, Question 3; See post for question

Yes, your answer is negative because you are dealing with the heat removed from the gas, each step will be negative and they will all be added together.
by Rachel Colbath 2G
Tue Feb 09, 2016 8:53 pm
Forum: Phase Changes & Related Calculations
Topic: 2014 Midterm Question 5C
Replies: 2
Views: 488

Re: 2014 Midterm Question 5C

E is not a state function: see this question
viewtopic.php?f=140&t=3754
by Rachel Colbath 2G
Tue Feb 09, 2016 8:22 pm
Forum: Phase Changes & Related Calculations
Topic: Winter 2013 Midterm Q2A.
Replies: 4
Views: 695

Re: Winter 2013 Midterm Q2A.

The ice is melting and cooling down the water. Delta H fusion will be positive because it is the melting enthalpy (the name is kind of confusing, it seems like delta H fusion would be freezing but it is melting)
by Rachel Colbath 2G
Sat Feb 06, 2016 11:06 am
Forum: Balancing Redox Reactions
Topic: Winter 2011 Midterm Q#6
Replies: 1
Views: 295

Winter 2011 Midterm Q#6

In this question we were asked to balance a redox reaction and got:

In the next step, we needed to calculate for Q, and 2Rb was excluded because it was a solid, but no states were given. Do we know how to assign states to the elements of a redox reaction?
by Rachel Colbath 2G
Fri Feb 05, 2016 12:11 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 8223
Views: 1435330

Re: Chemistry Jokes

The name's Bond
... Ionic Bond

"taken, not shared"
by Rachel Colbath 2G
Sun Jan 31, 2016 3:30 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Self Test 11.5A Standard Gibbs
Replies: 1
Views: 261

Self Test 11.5A Standard Gibbs

"Use the thermodynamic data in Appendix 2A to calculate K from the value of for the reaction
N204(g) -> 2NO2(g) at 298K."
Which element of the reaction do I look up for?
Is it delta G formation of NO2? If so, do I multiply that by 2?
by Rachel Colbath 2G
Fri Jan 22, 2016 11:33 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Homework Problem 9.19
Replies: 1
Views: 390

Homework Problem 9.19

9.19: "Calculate the standard entropy of vaporization of water at 85 degrees C, given that its standard entropy of vaporization at 100 degrees C is 109.0 J/K.mol and the molar heat capacities at constant pressure of liquid water and water vapor are 75.3 J/k.mol and 33.6 J/K.mol respectively in ...
by Rachel Colbath 2G
Mon Jan 18, 2016 12:01 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Constant Volume/Pressure Calorimeter
Replies: 1
Views: 884

Constant Volume/Pressure Calorimeter

What is the difference between a constant volume and a constant pressure calorimeter?
Are there different equations to solve for each?
by Rachel Colbath 2G
Fri Jan 15, 2016 7:10 pm
Forum: Calculating Work of Expansion
Topic: HW Problem 8.93 pressure of expansion
Replies: 2
Views: 490

HW Problem 8.93 pressure of expansion

8.93 part a states: "Calculate the work that must be done against atmosphere for the expansion of the gaseous products in the combustion of 1.00 mol C6H6 (l) at 25 degrees celsius and 1 bar" I understand that you solve for the moles of gas, and rearrange the work expansion equation as foll...
by Rachel Colbath 2G
Sun Jan 10, 2016 9:16 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Question 8.57
Replies: 1
Views: 354

Re: Question 8.57

I used this method as well, but you seem to have accidentally flipped products and reactants and somehow got it right. I did the following (-1560kJ)-[(-1300)+2(-286)] = 312 kJ (this is supposed to be negative) Is this a correct approach? If so, why are my signs not coming out correctly. The answer k...
by Rachel Colbath 2G
Sat Jan 09, 2016 8:24 pm
Forum: Phase Changes & Related Calculations
Topic: Homework Question 8.3
Replies: 3
Views: 1977

Re: Homework Question 8.3

In regards to part B of this question: (b) Is the work positive or negative with respect to the air in the pump? Is it correct to assume that the work is positive inside the pump because the gas is compressing and excerpting a greater force on the container as a result? Or it the work positive becau...
by Rachel Colbath 2G
Thu Nov 26, 2015 8:35 pm
Forum: Electron Configurations for Multi-Electron Atoms
Topic: Hund's Rule, Pauli Exclusion and Aufbau's Principle
Replies: 3
Views: 952

Re: Hund's Rule, Pauli Exclusion and Aufbau's Principle

Here is the video in .mov format. It describes electron configuration notation and includes definitions of Hund's Rule, Pauli exclusion, and the Aufbau Principle
by Rachel Colbath 2G
Mon Oct 26, 2015 11:47 pm
Forum: Bond Lengths & Energies
Topic: Unpaired electron bond dissociation
Replies: 1
Views: 384

Unpaired electron bond dissociation

I understand that a lone pair would weaken surrounding bonds, but how would an unpaired electron affect the dissociation energy?
by Rachel Colbath 2G
Sun Oct 25, 2015 4:15 pm
Forum: Administrative Questions and Class Announcements
Topic: Quiz #2 content
Replies: 1
Views: 405

Quiz #2 content

If Quiz #2 only covers Ch.3 and Ch.4 up through hybridization. Does that mean we aren't responsible for knowing how to do questions 4.51 on onward relating to molecular orbital theory? Should we complete the problems on the self quizzes related to bond order? Ex. #5 in the fall 2015 quiz 2 prep.
by Rachel Colbath 2G
Tue Oct 13, 2015 11:15 am
Forum: Photoelectric Effect
Topic: Fall 2013 Quiz Preperation Problem 10
Replies: 4
Views: 691

Re: Fall 2013 Quiz Preperation Problem 10

Do we keep track of sigfigs throughout the problem? ex. for the energy calculation I got for 1.023928759x10^-18 would I round that to 1.02x10^-18 considering it is limited by the given value 194 nm? Or do I plug in the whole value and only round according to sigfigs at the end. Also, I understand ho...
by Rachel Colbath 2G
Sun Oct 11, 2015 10:56 pm
Forum: Empirical & Molecular Formulas
Topic: Self Quiz Question 9
Replies: 1
Views: 316

Re: Self Quiz Question 9

You are on the right track. 2.38 can be multiplied by a whole number (a bit higher than 3) to get a whole number (it won't be exact, but close enough, within .1).
by Rachel Colbath 2G
Sun Oct 11, 2015 2:51 pm
Forum: Administrative Questions and Class Announcements
Topic: Chemical Nomenclature (quizzes)
Replies: 1
Views: 411

Chemical Nomenclature (quizzes)

I have minimal background in chemical nomenclature. Should we have the nomenclature of compounds in section D of the textbook committed to memory? Or are there some key common names for compounds that we should know for the upcoming quiz?
by Rachel Colbath 2G
Sun Oct 11, 2015 1:49 pm
Forum: Administrative Questions and Class Announcements
Topic: Practice Quiz for Quiz 1
Replies: 3
Views: 504

Re: Practice Quiz for Quiz 1

You turn your workbook in to your TA before you take the quiz.
by Rachel Colbath 2G
Sun Oct 04, 2015 6:49 pm
Forum: DeBroglie Equation
Topic: De Broglie wavelength: How small is too small?
Replies: 1
Views: 483

De Broglie wavelength: How small is too small?

At what point are wave lengths calculated by the De Broglie equation too small to be measured? I understand that you can't see the wavelike properties of the car used in the example. Is anything larger than an electron too small to be measured? Are we responsible for knowing where this cutoff is?
by Rachel Colbath 2G
Sat Sep 26, 2015 5:37 pm
Forum: Accuracy, Precision, Mole, Other Definitions
Topic: Calculating the sulfide of a metal
Replies: 4
Views: 734

Re: Calculating the sulfide of a metal [Calcium?]

I understand how to calculate for the mass of the unknown variable M, but when does the calcium become involved? The question asks for the mass of the sulfide, I thought that was S2-. The answer key is talking about the molar mass of calcium sulfide.

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