CHEMISTRY COMMUNITY

Rachel Colbath 2G

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...

Rachel Colbath 2G

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.

Rachel Colbath 2G

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 ...

Rachel Colbath 2G

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!

Rachel Colbath 2G

How would we know that the chlorine is bigger than the methyl group when arranging the second most stable conformation?

Rachel Colbath 2G

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?

Rachel Colbath 2G

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 ...

Rachel Colbath 2G

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...

Rachel Colbath 2G

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.

Rachel Colbath 2G

$E^{0}$ is an example of an intensive property
$\Delta H$ , $\Delta S$ are examples of extensive properties because they change with the size of the sample.

Rachel Colbath 2G

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.

Rachel Colbath 2G

E is not a state function: see this question
viewtopic.php?f=140&t=3754

Rachel Colbath 2G

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)

Rachel Colbath 2G

In this question we were asked to balance a redox reaction and got:
$F_{2}+2Rb \rightarrow 2F^-+2Rb^+$
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?

Rachel Colbath 2G

The name's Bond
... Ionic Bond

"taken, not shared"

Rachel Colbath 2G

"Use the thermodynamic data in Appendix 2A to calculate K from the value of $\Delta G_{r}^{0}$ for the reaction
N204(g) -> 2NO2(g) at 298K."
Which element of the reaction do I look up $\Delta G_{r}^{0}$ for?
Is it delta G formation of NO2? If so, do I multiply that by 2?

Rachel Colbath 2G

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 ...

Rachel Colbath 2G

What is the difference between a constant volume and a constant pressure calorimeter?
Are there different equations to solve for each?

Rachel Colbath 2G

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...

Rachel Colbath 2G

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...

Rachel Colbath 2G

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...

Rachel Colbath 2G

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

Rachel Colbath 2G

I understand that a lone pair would weaken surrounding bonds, but how would an unpaired electron affect the dissociation energy?

Rachel Colbath 2G

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.

Rachel Colbath 2G

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...

Rachel Colbath 2G

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).

Rachel Colbath 2G

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?

Rachel Colbath 2G

You turn your workbook in to your TA before you take the quiz.

Rachel Colbath 2G

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?

Rachel Colbath 2G

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 S^2-. The answer key is talking about the molar mass of calcium sulfide.

CHEMISTRY COMMUNITY

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Re: Winter 2013 Final Question 3A

Re: Cell Diagrams

Re: Winter 2011 Final Question

Priority naming - Alphabetical vs. # substituents

Re: Winter 2014 final question 7 part F newman projections

Vinyl and allyl groups

Reaction Profile Delta G

Re: M Calculations

Re: Winter 2015 Midterm Q1 heat

Re: Intensive/Extensive

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

Re: 2014 Midterm Question 5C

Re: Winter 2013 Midterm Q2A.

Winter 2011 Midterm Q#6

Re: Chemistry Jokes

Self Test 11.5A Standard Gibbs

Homework Problem 9.19

Constant Volume/Pressure Calorimeter

HW Problem 8.93 pressure of expansion

Re: Question 8.57

Re: Homework Question 8.3

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

Unpaired electron bond dissociation

Quiz #2 content

Re: Fall 2013 Quiz Preperation Problem 10

Re: Self Quiz Question 9

Chemical Nomenclature (quizzes)

Re: Practice Quiz for Quiz 1

De Broglie wavelength: How small is too small?

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