Search found 32 matches

by Tiffany 1B
Thu Mar 15, 2018 1:27 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: Catalysts
Replies: 2
Views: 129

Re: Catalysts

Catalysts aren't really consumed in the reaction since they are usually formed in a later state so that they can be used again and again. And I think the equilibrium isn't affected because both the forward and reverse rates are affected by the catalyst equally, since creates a new pathway. Hope that...
by Tiffany 1B
Thu Mar 15, 2018 1:18 am
Forum: *Alkanes
Topic: Chapter for O-Chem
Replies: 2
Views: 302

Re: Chapter for O-Chem

Chapter 19 and 20 are on O chem, so you might want to check those chapters. I think chapter 20 would be your best bet. Hope that helps.
by Tiffany 1B
Thu Mar 15, 2018 12:54 am
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: 14.13 d?
Replies: 1
Views: 94

Re: 14.13 d?

Hi,
I had a similar problem with this concept, but I think this has to do with the fact that the more positive cell potential (1.69>1.40)wants to be reduced more, so it becomes the cathode where the reduction occurs.. Hope this helps.
by Tiffany 1B
Thu Mar 15, 2018 12:18 am
Forum: Arrhenius Equation, Activation Energies, Catalysts
Topic: endothermic reaction.
Replies: 5
Views: 209

Re: endothermic reaction.

Hi,
I'm a little confused on how the Ea corresponds to whether the reaction is endothermic or exothermic. Can someone please explain this to me?
Thanks.
by Tiffany 1B
Wed Mar 14, 2018 11:28 pm
Forum: Administrative Questions and Class Announcements
Topic: Lavelle: Professor by day, wizard by night
Replies: 6
Views: 736

Re: Lavelle: Professor by day, wizard by night

Oh my haha. You don't see that everyday.
by Tiffany 1B
Sun Mar 11, 2018 3:29 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Heat Required to Heat a Substance
Replies: 5
Views: 210

Re: Heat Required to Heat a Substance

Hi, One of the easiest ways to determine this is the complexity of the molecule. In this case, butane has much more complexity. Hope that helps
by Tiffany 1B
Sun Mar 11, 2018 3:12 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Units
Replies: 3
Views: 196

Re: Units

Hi,
I think this is bc what youre finding is delta H rxn so per mole of product or whatever youre measuring, if I remember correctly. I think they said they wouldnt mark off points for using just kJ vs kJ/mol tho.. Hope that helps.
by Tiffany 1B
Sun Mar 11, 2018 2:45 pm
Forum: First Order Reactions
Topic: Log vs ln
Replies: 9
Views: 437

Re: Log vs ln

Yeah, I think you should just go with given equation. If you convert, you're adding an additional step where you could potentially introduce error.
by Tiffany 1B
Tue Mar 06, 2018 1:02 am
Forum: General Rate Laws
Topic: 15.19a Order
Replies: 6
Views: 212

Re: 15.19a Order

Yes, exactly what Beza was saying. You compare the two rate laws and their initial rates. Although the solutions manual does say 2&3 for the order of B you would actually use 1 and 3. So to solve for B it would look something like rate3/rate 1= [A]^l[B]^m[C]^n/[A]^l[B]^m[C]^n where everything wo...
by Tiffany 1B
Wed Feb 28, 2018 5:18 pm
Forum: Second Order Reactions
Topic: positive slope in second ordre graph
Replies: 2
Views: 131

Re: positive slope in second ordre graph

Hi, So I think the difference in these has to do with the way it is integrated, using the second order differential rate law (-1/a* d[A]/dt = k[A]^2) as starting point then separating variables and integrating using the power rule (which is in his integration rules tab on the website) you get -[A]^-...
by Tiffany 1B
Mon Feb 26, 2018 7:50 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7348
Views: 898521

Re: Post All Chemistry Jokes Here

If Avagadro calls, tell him to leave his number.
by Tiffany 1B
Mon Feb 26, 2018 7:45 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7348
Views: 898521

Re: Post All Chemistry Jokes Here

What is the chemical formula for banana?

BaNa^2
by Tiffany 1B
Wed Feb 21, 2018 8:18 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Reduction Half-Reactions
Replies: 2
Views: 112

Re: Reduction Half-Reactions

Hi,
So I believe this is because the equation itself accounts for the sign change, but as Ava said you can change the sign and then simply add them (instead of subtracting them). Hope that helps.
by Tiffany 1B
Wed Feb 21, 2018 8:11 pm
Forum: Galvanic/Voltaic Cells, Calculating Standard Cell Potentials, Cell Diagrams
Topic: Test 2
Replies: 2
Views: 126

Re: Test 2

Test 2 covers Chapter 14.1-14.11 so basically all of Electrochem. Hope that helps
by Tiffany 1B
Sun Feb 18, 2018 8:56 pm
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7348
Views: 898521

Re: Post All Chemistry Jokes Here

Why did the chemist coat his shoes with silicone?
-He wanted to reduce his carbon footprint.
by Tiffany 1B
Sun Feb 18, 2018 8:42 pm
Forum: Appications of the Nernst Equation (e.g., Concentration Cells, Non-Standard Cell Potentials, Calculating Equilibrium Constants and pH)
Topic: Q
Replies: 7
Views: 239

Re: Q

Yeah, Q is the concentrations of products over reactants just like K, except Q represents any point in the reaction while K is specifically at equilibrium.
by Tiffany 1B
Tue Feb 13, 2018 8:04 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: delta U for Isothermal Expansion of Ideal Gas
Replies: 2
Views: 150

Re: delta U for Isothermal Expansion of Ideal Gas

The equation for an ideal gas is U=3/2*nRT. When you're calculating the change in internal energy, the number of moles and the gas constant are constant values and that means the change in internal energy is dependent upon temperature change. But in an isothermal expansion temperature doesn't change...
by Tiffany 1B
Sat Feb 10, 2018 8:53 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: ∆S=q/T and irreversible reactions
Replies: 2
Views: 103

Re: ∆S=q/T and irreversible reactions

Yeah, since it's a state function the 'path' it took to get from initial to final doesn't matter so you could use the reversible path and that equation to solve for the irreversible. I think the book goes over this idea in more depth in the first few pages of chapter 9 as well. Hope that helps.
by Tiffany 1B
Sat Feb 10, 2018 8:45 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: deltaG=0, Phases Coexist ?
Replies: 2
Views: 136

Re: deltaG=0, Phases Coexist ?

Hi,
Yeah so since at boiling point the particles don't have a higher tendency to go to liquid over gas or vice versa, you could just imagine some particles as gas and others as a liquid at this point. Hope that helps.
by Tiffany 1B
Sat Feb 10, 2018 8:41 pm
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Calculating Gibbs Free Energy [ENDORSED]
Replies: 2
Views: 137

Re: Calculating Gibbs Free Energy [ENDORSED]

Hi, So I think the first one is used for any constant temperature while the standard Gibbs free energy is used when both the products and reactants are in their standard states at one bar and the temp(which I think is) 298K. Other than that I'd say just using what you're given is main way to tell. H...
by Tiffany 1B
Sun Feb 04, 2018 10:05 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7348
Views: 898521

Re: Post All Chemistry Jokes Here

What type of dog do chemists have?
Laboratory Retrievers
by Tiffany 1B
Sun Feb 04, 2018 9:58 am
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Isolated
Replies: 9
Views: 347

Re: Isolated

I think this would be because the heat is contained within the system.
by Tiffany 1B
Sun Feb 04, 2018 9:50 am
Forum: Gibbs Free Energy Concepts and Calculations
Topic: Spontaneity
Replies: 4
Views: 135

Re: Spontaneity

Yes, bc delta G takes into account both enthalpy and entropy, the two factors Dr. Lavelle said were needed to determine spontaneity. If delta G is negative, then it's spontaneous. Hope that helps.
by Tiffany 1B
Sat Jan 27, 2018 6:47 pm
Forum: Calculating Work of Expansion
Topic: equation
Replies: 2
Views: 109

Re: equation

Hi, So the difference of when to use those two equations is whether or not the pressure is constant. If the pressure is a constant than you would use the w=-p delta V. If the pressure isn't a constant you would use the w=-nRT ln(v2/v1). Dr. Lavelle showed us how to derive them on the 24th I think if...
by Tiffany 1B
Sat Jan 27, 2018 6:27 pm
Forum: Administrative Questions and Class Announcements
Topic: Out of Topic
Replies: 3
Views: 217

Re: Out of Topic

Yeah, definitely check the syllabus and the TA and UA hours as well because if you cant do Dr. Lavelle's hours there are a some that would work for your schedule.
by Tiffany 1B
Sat Jan 27, 2018 6:19 pm
Forum: Concepts & Calculations Using Second Law of Thermodynamics
Topic: Spontaneous [ENDORSED]
Replies: 6
Views: 186

Re: Spontaneous [ENDORSED]

Yeah so with spontaneous processes the entropy does increase so I think you would probably be able to assume that a positive delta S means spontaneous. Although Gibbs free energy might be a more definite way...
by Tiffany 1B
Sun Jan 21, 2018 2:49 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7348
Views: 898521

Re: Post All Chemistry Jokes Here

"Thermodynamics just gets me so q-ed"
-Frustrated chem students everywhere
by Tiffany 1B
Sun Jan 21, 2018 2:27 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: 8.51
Replies: 5
Views: 181

Re: 8.51

DamianW, Something being in its "most stable form" refers to it being in its 'most pure/most stable' state, which I like to think of as how you would normally find it; an example of this would be oxygen which we know is all around us in the form of O2. In this particular problem, we know t...
by Tiffany 1B
Mon Jan 15, 2018 9:20 pm
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Q 8.11
Replies: 1
Views: 84

Re: Q 8.11

Hi. So I think the difference between the R value of 0.08206 or (0.0821) and the R value the book used is the pressure unit. The R=8.314 is using kPa vs the R= 0.0821 is using atm Straight from my constant sheet from last quarter: R = 8.314 L ∙ kPa ∙ K−1∙ mol−1 R = 0.08206 L ∙ atm ∙ K−1∙ mol−1 Hope ...
by Tiffany 1B
Sun Jan 14, 2018 9:08 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Most Staple Phases
Replies: 3
Views: 123

Re: Most Staple Phases

Yeah those are the only ones I have written down as well. Carbon as graphite, I2 as a solid,Br2 as liquid and the others diatomic ones(N2, F2,O2 Cl2) as gases.
by Tiffany 1B
Sun Jan 14, 2018 8:58 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: Molar Heat Capacity
Replies: 4
Views: 108

Re: Molar Heat Capacity

Yeah I think so because molar heat capacity is given by Q=nC Delta T so the higher number of moles, the greater the heat capacity you should get/expect.
by Tiffany 1B
Wed Jan 10, 2018 6:14 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: What is bond enthalpy and can someone explain to me what Lavelle was doing with the Lewis Structures in today's lecture?
Replies: 3
Views: 130

Re: What is bond enthalpy and can someone explain to me what Lavelle was doing with the Lewis Structures in today's lect

Yeah exactly what Daniisaacson2F was saying. Using the bond enthalpies was just an alternative to the first method w/ Hess's Law. The bonds that were broken were the C=C bond and the H-Br bond and the ones formed/ rearranged were the C-C, C-H, C-Br bonds. Then he used the bond enthalpy values(knowin...

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