Search found 22 matches

by Angela_Pu_3C
Fri Mar 17, 2017 6:34 pm
Forum: *Cycloalkenes
Topic: Naming cyclodienes
Replies: 1
Views: 672

Naming cyclodienes

On pg 29 of intro to orgo, the ex under "unconjugated dienes" reads as "Cyclo hex -1,4-diene." However, for self-test 1.11A part B (on the bottom of the same page), the answer reads as "1,6-Dimethylcyclo hexa -1,4-diene." Pg 30 continues with ex like "cyclo octa -1...
by Angela_Pu_3C
Sun Mar 05, 2017 4:42 pm
Forum: *Free Energy of Activation vs Activation Energy
Topic: Potential Energy and Gibbs free energy reaction Profile
Replies: 1
Views: 715

Potential Energy and Gibbs free energy reaction Profile

On pg 157, the intro to orgo book says that the standard gibbs free energy of activation for both transition steps will be bw the transition states and reactants bc "it is more convenient to determine all diff w respect to the reactants." Could someone please explain why it's more convenie...
by Angela_Pu_3C
Sun Mar 05, 2017 4:30 pm
Forum: *Free Energy of Activation vs Activation Energy
Topic: Self Test 4.4A part c
Replies: 1
Views: 709

Self Test 4.4A part c

In this it says that given the graph, step one would have the larger Ea, but how can you tell that? I kinda assumed that since the standard gibbs free energy of activation was larger in the second step, it would have the larger Ea. Thanks :)
by Angela_Pu_3C
Wed Mar 01, 2017 1:35 am
Forum: *Nucleophiles
Topic: Double Bond Nucleophile
Replies: 1
Views: 250

Double Bond Nucleophile

On pg 152 of Intro to OChem there is an ex w two steps. The first step displays propene and Hydrogen bromide. In the description for this step it says that propene is the nucleophile, but shouldn't the double bond in propene be labeled the nucleophile. Idk if this is technical or what bc it's more s...
by Angela_Pu_3C
Wed Feb 15, 2017 2:08 am
Forum: Third Law of Thermodynamics (For a Unique Ground State (W=1): S -> 0 as T -> 0) and Calculations Using Boltzmann Equation for Entropy
Topic: Midterm Winter 2013 problem 5B
Replies: 10
Views: 953

Re: Midterm Winter 2013 problem 5B

CH4 has highest STANDARD molar entropy bc it has highest mass. When the molecule is heavier, its vibrational energy is higher, so it has more entropy. You look at atom positions when you're looking at RESIDUAL entropy. This is when the molecules are given at T=0K. In this case, for ex CH4 and CF4 wo...
by Angela_Pu_3C
Tue Feb 14, 2017 1:03 am
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: w=-delta(nRT)
Replies: 2
Views: 628

w=-delta(nRT)

For w=-delta(nRT), is it the change in moles or temperature? I've read the posts here and they've had different answers. Thanks :)
by Angela_Pu_3C
Mon Feb 06, 2017 3:07 am
Forum: Student Social/Study Group
Topic: Post All Chemistry Jokes Here
Replies: 7741
Views: 1059396

Re: Post All Chemistry Jokes Here

Chemjoke.png
by Angela_Pu_3C
Sun Jan 29, 2017 9:54 pm
Forum: Heat Capacities, Calorimeters & Calorimetry Calculations
Topic: HW Ch. 8 #41
Replies: 1
Views: 232

Re: HW Ch. 8 #41

q=mC(Tfinal-Tinitial)
heat lost by water (-q)=(q) heat heat gained by ice

-mC(Tf-Ti)=mC(Tf-Ti)+n(deltaH fusion of ice)


What you're missing is the mC(Tf-Ti) for ice. Once included you'll get:

-400g(4.184J/Cg)(Tfinal-45C)=50g(4.184J/Cg)(Tfinal-0C)+2.8mol(6010 J/mol)
And so Tfinal=31C
by Angela_Pu_3C
Mon Jan 23, 2017 2:10 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Enthalpy and Internal Energy relationship
Replies: 1
Views: 334

Re: Enthalpy and Internal Energy relationship

The change in internal energy(ΔU) is a a combo of energy transferred from heating(q) and compression(w). When at a constant pressure, q can be equivalent to the change in enthalpy(ΔH), being heat released or absorbed at constant P. So increasing/decreasing ΔH will inc/dec ΔU accordingly. When the rx...
by Angela_Pu_3C
Sun Jan 15, 2017 10:12 pm
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Bond Enthalpy versus standard Enthalpies of formation
Replies: 2
Views: 290

Re: Bond Enthalpy versus standard Enthalpies of formation

Based on the textbook problems Lavelle assigned, the problem may tell you which method it wants you to use. If not, I'm p sure that you'll be provided w certain info (aka standard enthalpies of formation or bond enthalpies) which will push you towards using a certain method, and you'll solve the pro...
by Angela_Pu_3C
Mon Nov 28, 2016 9:10 pm
Forum: Bronsted Acids & Bases
Topic: Common Acids/Bases
Replies: 3
Views: 391

Re: Common Acids/Bases

I don't think we need to memorize them per se, but rather generally recognize which acids & bases are strong/weak.
by Angela_Pu_3C
Mon Nov 28, 2016 8:30 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Negligible x given a small K value
Replies: 1
Views: 235

Negligible x given a small K value

What's the largest K value that can be considered a small K (leading to a small x, allowing you to approximate your concentrations)?
by Angela_Pu_3C
Mon Nov 28, 2016 7:58 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework 11.41
Replies: 3
Views: 343

Re: Homework 11.41

Yeah I realized I forgot a conversion thank you!
by Angela_Pu_3C
Mon Nov 28, 2016 7:37 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework 11.41
Replies: 3
Views: 343

Homework 11.41

Why do we plug in 1.581x10-3? The x (or molar concentration of CO2) is 1.581M (resulting in Kc=1.58) so I'm not sure how/why we use 1.581x10-3 instead. Thank you!
by Angela_Pu_3C
Mon Nov 28, 2016 1:21 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Homework Problem 11.41
Replies: 3
Views: 850

Re: Homework Problem 11.41

Why do we plug in 1.581x10-3? The x (or molar concentration of CO2) is 1.581M (resulting in Kc=1.58) so I'm not sure how/why we use 1.581x10-3 instead.
by Angela_Pu_3C
Wed Nov 02, 2016 12:38 am
Forum: Lewis Structures
Topic: Homework 3.95
Replies: 1
Views: 228

Re: Homework 3.95

If you draw out the whole molecule, you'll see that for a non-central Carbon atom that is attached to the central Carbon with a single bond, the Carbon has a FC=4-(2+3)=-1. The -1 FC of CH2 is based off of the Carbon atom. (The two H atoms each have a FC of 0)
by Angela_Pu_3C
Sun Oct 30, 2016 4:35 pm
Forum: Lewis Structures
Topic: Ch 3 question 97
Replies: 1
Views: 248

Ch 3 question 97

How is P4 a tetrahedral molecule? It only has 4 atoms and creates a kite shape.
by Angela_Pu_3C
Fri Oct 28, 2016 9:53 pm
Forum: *Molecular Orbital Theory (Bond Order, Diamagnetism, Paramagnetism)
Topic: Midterm
Replies: 9
Views: 722

Re: Midterm

All material covered in Fundamentals and Chapters 1-4 up to the end of hybridization.
Course Reader: All material up to page 105.
Past Midterms in Course Reader: Pages 179-217

For more info go to this link: viewtopic.php?f=157&t=16342
by Angela_Pu_3C
Fri Oct 21, 2016 2:25 am
Forum: Quantum Numbers and The H-Atom
Topic: Ch 2.1
Replies: 1
Views: 302

Ch 2.1

In the textbook it says, "The difference in energy between the ground state and the ionized state is the energy required to remove an electron from the neutral atom in its ground state. The ionization energy itself...is the minimum energy needed to achieve ionization, with the electron removed ...
by Angela_Pu_3C
Thu Oct 13, 2016 8:26 pm
Forum: Bohr Frequency Condition, H-Atom , Atomic Spectroscopy
Topic: Practice Quiz #8
Replies: 2
Views: 341

Re: Practice Quiz #8

When the electron transitions fro n=4 to n=3, energy is emitted. So in the equation E=-hR((1/nfinal^2)-(1/ninitial^2)), E becomes -E, and you'll find that after substituting in your numbers your answer will be positive.

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