CHEMISTRY COMMUNITY

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by the same side- i mean if you draw out the chair conformation- and the 2 substituents are both on the top half of the drawing-

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"you can say that, if you have the q for the reaction at lower temp. (like this particular example)
So if you know the q for the reaction at higher temp instead,"

- what do you mean- lower temperature than what???

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so double bond gets priority- right

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so even if they are on the same side- but one is pointing up and one is pointing down- its trans?

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then how do you know when to overlap the 2 main groups??

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so if you don't have the enthalpies- you always just cool the reactants, find kj of reactant, and then heat the products??

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oh- so the H2 cancelled out means that its accepting the electrons

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and you find ph by doing 10^-(concentration of H) right?

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how can you tell if a cyclohexane is cis or trans?

is it if its on the same side? or is it cis if the axial and equatorial are both pointing in the same direction???

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Question 6A on the Winter 2013 Final Exam states: "Carotenes are usually orange or yellow in color and play a role in photosynthesis by transmitting the light energy they absorb from chlorophyll. Part of a carotene molecule is below. Name it, identify (circle) the sp2 carbon atoms, and give its...

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Question 8A on the Winter 2012 Final Exam states:

"Draw a Newman projection of 1 -iodopropane looking down the C1-C2 bond with a dihedral angle of +120 degrees for the ICCC dihedral angle."

8A would be eclipsed when the CH3 is behind the I?

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Question 8A on the Winter 2012 Final Exam states: "Draw a Newman projection of 1 -iodopropane looking down the C1-C2 bond with a dihedral angle of +120 degrees for the ICCC dihedral angle." In the answer key it says it needs to be eclipsed. Does that mean that 120 degrees is eclipsed? Also...

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where do get the 3 from ( how do you know how to multiply it by 3)

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how do you know to heat the products and cool the reactants?

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how do you know to take out H- is that because you can only find pH with H+?

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how do they get z-octadec9-enoic acid

why is it 9? i thought it was 7?

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at what pH would the concentrations listed above be in equilibrium at 298k?

where did they get the 1.67 from???

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what about if you want to find the kb value is it also electrolysis?
also you know for ka you have to do the square root of K

do you also have to do that for kb?

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will the problem tell us its electrolysis? or how would we recognize an electrolysis problem?

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how much work does 100g of water do when it freezes at 0 degrees and pushes back the plastic wall of a pipe that exerts an opposing pressure of 1070 atm? density of water i 1g/cm^3 and density of ice is .92g/cm^3

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how will adding water to anode compartment effect cell potential? also adding water to cathode?

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thanks-
when do we want the overall E to be negative?

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how do you relate degree of strain to size of a ring?

is it the more carbons- the less strain?

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how do you figure out the dihedral angle?
also why does potential energy depend on dihedral angle?

also how do you determine the relative conformational stabilities of di-substitued and try-subsituted cyclohexanes?

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is F an electrophile and F- a nucleophile?
only if it has negative charge on F will it be nucleophile?

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how do you now if CrCl3 or CuSo4 is an anode/ cathode? how can you tell which is which??

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Question 7E on the Winter 2010 Final Exam states: "Give the IUPAC names for: propylamine ________________ 1-propanamine isopropylamine ______________2-propanamine methyl ethyl amine ____________N-methylethanamine trimethylamine _______________N, N-dimethylmethanamine" how do you give upac ...

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do molecules with more carbons in a ring have more or less ring strain than molecules with less carbons in a ring?

cause on 4c on test2011 it stays that the ring strain of the cyclooctane has higher ring strain than cyclohexane-

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that makes so much for sense!

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also i undestand in this problem which is the anode and the cathode- i don't understand what is the electrode for both the anode and cathode

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then how come on the last problem of the final. they made the cell potential negative instead of positive- i don't understand why

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Question 6B on the Winter 2007 Final Exam states: "Draw a structure which clearly shows the most stable conformation for 1-ethyl-1-isopropylcyclohexane." i know its a chair but how do you know which to put in axial in which to put in equatorial. also is the molecular formula for isopropyl ...

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but they don't give us the specific heat capacity of copper. how would we figure it out without that?

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thanks! It also asks which electrode in each cell is the anode
for pb it says Pb (s) and I understand that because its a solid. but for Cu its the standard hydrogen electrode- why isn't it the Cu(s)????

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2Fe + 2h20 + 02 - 2Fe(OH)2
how do you know that n=4???

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do we also have to know all the angles for each drawing? also do we have to memorize the energies for each conformation (like know the torsional strain for a specific conformation)??

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how do you find the k? if you only have the concentration but not the rate???

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on heating from 10 to 20 celsius which requires mor heat?
its water

which requires more heat
breaking c-c single bonds or melting 1 mole of ice
its breaking bond

how do you know these things??

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b. which electrode in each cell is the anode?

how do you figure this out?

for pb its pb (s)
for cu cell its the standard H electrode

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is this type of fuel cell thermodynamically feasible?
the answer is yes

what makes something thermodynamically feasible?????

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do we have to know how to draw everything- like all the structures (boat, chair, ect. knowing where all the H's go)
how do you know which newman projection is the most stable for a particular molecule?

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what is the E (Knot) of each cell at 298?

how do you find the E knot of the Pb and Cu at a certain temperature?
do they automatically just become positive???

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1,1, bromochlorocyclohexane has a preference for 1 conformation, draw it and draw it undergoing a ring flip

how do you know which preference it has?
is it a chair????

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how can you tell without drawing it - if it has torsional or steric strain

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http://web.tock.com/kalee/chem32/groupT/ethane.gif

on the top 2 pictures- how do you know which one is eclipsed or staggered- i don't understand how you can differentiate them

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name of the reaction mechanism for reaction CH3Br + OH - CH3OH + Br-
its bimolecular nucleophili substitution reaction SN2.

do you know that just by looking at it, or do you have to draw a lewis structure?

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30. the Ea in the organic reaction is 125 kj/mol. will reaction occur at room temperature?
the answer is no,
but why??? how do you know?

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in class on friday he said the name of something was dimethyl ethyl cyclohexane.
I thought its supposed to be in alphabetical order and be ethyl dimethyl cyclohexane (cause I thought the di in front didn't count)

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where are the detailed solutions- I can't find them?

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randome question i found

a zero order reaction is 40% complete in 200.s. how long does it rake for 15% completion (use (A)0= .100M

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thanks- does temperature also affect the orders?

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how do you know just by looking at a graph if its spontaneous?
how do you know just by looking at a graph if it favors the reactant or product?
how do you know just by looking at a graph if its thermodynamically unfavorable?

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what happens to a second order reaction as the concentration doubles?

are all the orders dependent on concentration? zero isn't right?
what else are the order dependent on?

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i am a little confused with some parts of your answer
like this- are you saying its linear or not??

(e) k vs t
Lnk = -Ea/(RT) + Ln[A] = -(Ea/R)(1/T) + Ln[A]

NOT LINEAR: Lnk vs 1/T would be linear

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how do you know if something is linear under certain conditions?
like in question 103 when it asks a bunch of scenarios- like if 1/A is it linear in first condition, or half life and temperature if its linear??

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Thanks!

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how do you draw a proposed structure for the activated complex

1. CH3CHO- CH3 + CHO
2. r=k (I2)(Ar) 2I- I 2
3. O2 + NO - NO2 + O

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the rate constant for a first order redaction is .76 s-1 at 1000K and .85 s-1 at 1030K. calculate activation energy

how are you supposed to know which is k and which is k' ????

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If there is no reverse reaction- it is usually a slow step.
the fast reactions, also have reverse reactions.

thats just one clue

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The throughs represent the transition states. They have the most energy right? Do the intermediates also have a lot of energy?

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Thanks! the larger the peak- it means the more activation energy needed right? Also the higher the peak- the more likely to have a catalyst right?

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there is one problem that I saw where there is an intermediate and a catalyst- in a multistep reaction
you can see both the catalyst and the intermediate in the equations- but they both get crossed out

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how can you tell by looking at a graph, how many intermediates there will be??

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what does radical chain initiating mean? and does it occur when the concentration is squared?

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what does the R stand for in the activation energy equation? How do you find its value?

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how can you determine which is the intermediate and which is the catalyst in a reaction?

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is q always negative for combustion??

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yeah for this one thats not the case- because reversing it gives you a negative number

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how do you know that F2 +H+ +2e- - 2HF is the anode????

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why is it squared?

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what would be the effect on the cell potential if you added water to the anode compartment??
or the cathode??

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where does the random 1.101325^2 come from??

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for lnk is K product/reactant or is it anode/cathode???

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i saw the same thing! I think its a mistake!

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isn't the number of moles for H2/H+ 2? in the answers its only one??

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so if something occurs in a bomb calorimeter and then asks what the delta U is for reaction. i know w =0, but would q become negative- cause of the surrounding/system idea??

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thanks so much! so whenever it is that equation with the C we use 3/2 when its a constant volume?

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why is this the order of increasing residual entropy???

C2H2<HF<BCl2H

i would think that HF is the least??? so confused!

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I know that part. But for only some questions do people put it in. like for entropy- only sometimes is 3/2 put in. Is it only when we have two temperatures that we are given? because when we are given two volumes- they never put 3/2R

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how do you predict if a metal will dissolve in a solution?

does that mean- dissolve would that be oxidation or reduction?

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Understand the environmental impact of burning fossil fuels and use of alternative fuels

what do we have to know for this?

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yeah thats what i thought to but on midterm 2013 number 5B.
they say that the increasing molar entropy is
CH3F<CH2F2<CHF3<CF4

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how would you Predict the effect of changes in concentration of reactants and products on the cell potential

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when do you use the 3/2 R in the entropy equations??

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Can lead produce zinc metal from aqueous zinc sulfate under standard conditions?

what is this question asking? is it asking if lead can be oxidized or reduced?

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heating the water they do the q=mcchangeT + Hvap of water
for the Hvap of water they get 2259J/g- where do they get that number- i thought it was 40.7kj/mol??

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calculate free energy at 25 for combustion of 1 mol of glucose change in G=change in H- T change in S they give you change in H (subscript C)= -2808kj/mol what does the subscript stand for in the answer they use this as the change in H, but i thought you have to do products- reactants. so the H of H...

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how do you know the order of increasing molar entropy for the following gases

CH3F CF4 CH3F CH2F2

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balance redox reaction that occurs in acid

Cr2O7^2- + H2(g) - Cr^3+ (aq)

i understand that you need to add H+

but when you balance how do you know what coefficient to put in front of the H2 and how many to put in front of the H+, because they are both H's

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during your camping weekend you use 2 moles of butane gas for cooking. the enthalpy of combustion is -2878 kj/mol. assume reaction occurs at 300 degrees celsius and constant pressure of 1atm. in the solutions they find the that moles goes from 15 to 18 and they get a change of moles is 3. where do t...

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what affects cell potentials?
adding water? adding mass? to cathode/anode
what else effects it and how?

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do we have to know that AgOH forms an insoluble precipitate- what does that even mean?

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write balanced half reactions for the redox reactions of an acidified solution of potassium permanganate and iron II chloride. b. write balanced equation and cell diagram in the solutions they have the half equations for MnO4 and Fe3+, but there is no mention of potassium or chloride. what happened ...

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show how change in S is related to change in H at constant temperature

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Explain how temperature, volume and state of matter affect the entropy of a substance

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why does reaction free energy depends on pressure and the equilibrium constant?

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also there is a t in cathode- so you could think of that as positive

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when writing cell diagrams- which electrode should we use? I saw that you can use Pt(s) and C(s)- does it matter what one you use?

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work done on the system is positive.it is usually a gas doing a work on the system. but work done by the system would be negative work.

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what does the Pt(s) stand for in the cell diagrams. what is the difference if they are in the front or the back of the equations?

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