Search found 25 matches

by Marie_Bae_3M
Tue Mar 14, 2017 1:08 am
Forum: Calculating Work of Expansion
Topic: Midterm 2013 Q4A
Replies: 3
Views: 397

Re: Midterm 2013 Q4A

Yes, I believe you can use either one. w=-nRTln(p1/p2) is basically found from the original w=-nRTln(v2/v1). This goes back to boyle's law p1v1=p2v2. In other words, v2/v1=p1/p2 (pressure and volume are inversely related to each other) and you plug this into the original equation.
by Marie_Bae_3M
Thu Mar 09, 2017 11:55 pm
Forum: Reaction Mechanisms, Reaction Profiles
Topic: Relationship between activation energy and pseudo delta g
Replies: 2
Views: 720

Relationship between activation energy and pseudo delta g

I used to think that pseudo delta g (as the gibbs free energy of activation) was related to the activation energy (Ea), but it was pointed out that in a reaction profile, pseudo delta g would depend on the difference between reactants' deltaG and transition state's deltaG and Ea would would depend o...
by Marie_Bae_3M
Fri Mar 03, 2017 12:11 am
Forum: *Alkanes
Topic: Line structures
Replies: 1
Views: 180

Re: Line structures

I think if they vary in length they have to do with the number of bonds (ie: single, double, triple bonds). Triple bonds would be the shortest because the molecules bonded together are more firmly held together, therefore closer to each other, resulting in shorter bond length. However, I think in th...
by Marie_Bae_3M
Fri Feb 24, 2017 11:33 pm
Forum: General Rate Laws
Topic: 15.5 Positive vs Negative
Replies: 2
Views: 321

Re: 15.5 Positive vs Negative

I'm not completely sure but I think the negative in the rate of decomposition for O2 (-d[O2]/dt) is in terms of the general reaction rate and merely indicates that the concentration of O2 is being used up. Since "reacts" already implies the negative (O2 concentration decreasing), I think a...
by Marie_Bae_3M
Fri Feb 17, 2017 1:27 pm
Forum: General Rate Laws
Topic: Homework Help 15.1
Replies: 4
Views: 433

Re: Homework Help 15.1

I'm not entirely sure but I used the method of initial rates: -1/a*(d[A]/dt)=1/b*(d[B]/dt)=1/c*(d[C]/dt) for aA ------> bB+cC. In this case, I did: -1/1*(d[N2]/dt)=-1/3(d[H2]/dt) Cancel out the dt's and the -1's. Then you are left with d[N2] (which is the rate of the concentration on N2) = 1/3*d[H2]...
by Marie_Bae_3M
Sat Feb 11, 2017 8:21 pm
Forum: Student Social/Study Group
Topic: Study Group for Midterm Winter 2017
Replies: 2
Views: 369

Re: Study Group for Midterm Winter 2017

I'd love to!! How does Monday night sound to you? :)
by Marie_Bae_3M
Sat Feb 11, 2017 10:20 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.27
Replies: 3
Views: 256

Re: 14.27

I think you just have the E potentials mixed up. U+3+3e-->U is E=-1.79, U+4+e-->U+3 is E=-.61
by Marie_Bae_3M
Fri Feb 10, 2017 1:45 am
Forum: Work, Gibbs Free Energy, Cell (Redox) Potentials
Topic: 14.27
Replies: 3
Views: 256

Re: 14.27

I think that, in this case, we cannot add the E*'s together because the number of moles of electrons are not the same in the half-reactions (1e- vs. 3e-). According to the solutions manual, we have to use the deltaG*=-nFE* equation, to find the deltaG* of each individual half-reaction. Then we add t...
by Marie_Bae_3M
Mon Jan 30, 2017 1:30 am
Forum: Reaction Enthalpies (e.g., Using Hess’s Law, Bond Enthalpies, Standard Enthalpies of Formation)
Topic: Homework 8.41
Replies: 1
Views: 268

Re: Homework 8.41

I think it might be just because of rounding. Some of the problems I've been doing were off by about 0.2 when i used 8.314 J/(K*mol) instead of 8.32 J/(K*mol) from the solution guide, considering that there's also multiplication of huge numbers involved in this question too. I actually got 31 celsiu...
by Marie_Bae_3M
Thu Jan 26, 2017 7:25 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Reversible Reaction
Replies: 1
Views: 207

Re: Reversible Reaction

A reversible reaction is a process in which the direction can be "reversed" by infinitesimal changes in some property of the system via its surroundings, without actually increasing entropy.
by Marie_Bae_3M
Tue Jan 24, 2017 9:58 am
Forum: Concepts & Calculations Using First Law of Thermodynamics
Topic: Molar Heat Capacity
Replies: 2
Views: 291

Re: Molar Heat Capacity

I'm not sure if this is what you meant, but the ideal gas law is PV=nRT. In other words n=PV/(RT). If we plug in PV/(RT) into the molar heat = moles * molar heat capacity* change in temperature, molar heat capacity=molar heat / ((PV/(RT))*change in temperature)=molar heat*RT/(PV*change in temperatur...
by Marie_Bae_3M
Fri Jan 20, 2017 2:00 am
Forum: Phase Changes & Related Calculations
Topic: Chapter 8 Question 11 Part B [ENDORSED]
Replies: 1
Views: 203

Re: Chapter 8 Question 11 Part B [ENDORSED]

I think that "isothermal" (constant temperature) "reversible" expansion was meant to emphasize a certain work equation we have to use: w = -nRTln(Vfinal/Vinitial)? "Isothermal" in that as a gas expands (increase in volume), the gas's pressure decreases, as stated by Boy...
by Marie_Bae_3M
Fri Jan 13, 2017 1:32 pm
Forum: Thermodynamic Systems (Open, Closed, Isolated)
Topic: Calorimeters
Replies: 3
Views: 353

Calorimeters

I just wanted to be certain about the type of system that calorimeters are? So, all calorimeters act as isolated systems because they have to be thermally insulated, right? I was confused because calorimeters measure the transfer of energy as heat, so couldn't it be a closed system? Thank you!
by Marie_Bae_3M
Fri Dec 02, 2016 12:26 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: 2nd Final 2007 Q4C
Replies: 1
Views: 289

2nd Final 2007 Q4C

The equil. constant Kc equals 0.045 at 250C for the decomposition reaction PCl5 <--> PCl3 + Cl2 Calculate the percentage of PCl5 that disassociates if 0.05 mole of PCl5 is placed in a closed vessel (constant volume) at 250C abd 2.00atm pressure.. what i tried to do was find molar concentration by fi...
by Marie_Bae_3M
Tue Nov 29, 2016 11:11 pm
Forum: General Science Questions
Topic: Sig Figs
Replies: 3
Views: 665

Re: Sig Figs

The way I learned it was not to round until the final value because otherwise the rounded value at each step can become very different from the actual value?
by Marie_Bae_3M
Fri Nov 25, 2016 8:32 pm
Forum: Non-Equilibrium Conditions & The Reaction Quotient
Topic: 11.13
Replies: 2
Views: 404

Re: 11.13

I think that since parts a and c involved gases only, it used partial pressures (P)? Since part b involved only aqueous solutions, it used molar concentrations instead ([])?
by Marie_Bae_3M
Mon Nov 14, 2016 4:49 pm
Forum: Equilibrium Constants & Calculating Concentrations
Topic: Equil. Constants and Temperature
Replies: 1
Views: 280

Equil. Constants and Temperature

So, if K changes with temperature, then how is that shown with the equilibrium constant expression? Is it based on the P=MRT equation and the molar concentration changes, so the equil. constant also changes, or is there another equation that relates equil. constants and temperature?
by Marie_Bae_3M
Sun Nov 13, 2016 3:40 pm
Forum: Bond Lengths & Energies
Topic: Question 5B Midterm
Replies: 1
Views: 539

Re: Question 5B Midterm

I think this is because n = 3 refers to the 3rd orbital. l = 2 refers to the d-orbital. So, the subshell notation becomes 3d orbital, and the d-orbital contains 5 orbitals. :)
by Marie_Bae_3M
Wed Nov 02, 2016 10:09 am
Forum: Dipole Moments
Topic: Polar and Non-polar bond
Replies: 8
Views: 926

Re: Polar and Non-polar bond

I don't think we have to know the exact values... just the general trend to find out which is more electronegative than the other. Also, the electronegativities given in the book are a bit different from the ones from my ap chem teacher and online so i dont think they'll be that specific as to findi...
by Marie_Bae_3M
Sun Oct 30, 2016 1:05 pm
Forum: Dipole Moments
Topic: Polar and Non-polar bond
Replies: 8
Views: 926

Re: Polar and Non-polar bond

I believe you can find whether a bond is polar or not by determining the difference in the electronegativities of the atoms being bonded. For example, Na-F is polar because Fluorine's electronegativity of 4.0 - Sodium's electronegativity of 0.93 = a huge polarity of 3.07. To determine whether the po...
by Marie_Bae_3M
Thu Oct 27, 2016 8:59 pm
Forum: Determining Molecular Shape (VSEPR)
Topic: VSPER Model [ENDORSED]
Replies: 2
Views: 308

Re: VSPER Model [ENDORSED]

Yes, I believe they mean the same thing :)
by Marie_Bae_3M
Wed Oct 19, 2016 4:33 pm
Forum: Lewis Structures
Topic: Formal Charge vs. Octet [ENDORSED]
Replies: 1
Views: 311

Formal Charge vs. Octet [ENDORSED]

Which is more stable for BF3, as it is with FC all equaling 0 or as a coordinate covalent bond (because boron's formal charge would no longer be 0 then?)?
If the former, why would BF3 react in the first place if it's already stable?

Thank you!!
by Marie_Bae_3M
Fri Oct 14, 2016 1:47 pm
Forum: Wave Functions and s-, p-, d-, f- Orbitals
Topic: Electron configuration representation
Replies: 1
Views: 225

Electron configuration representation

Hi,
Does it matter whether we have to use the previous noble gas in brackets to shorten the e- configuration representation of an element X or if we could use any element prior to that element X? Thanks :)
by Marie_Bae_3M
Fri Oct 07, 2016 1:19 pm
Forum: Properties of Electrons
Topic: Chapter 1 HW Question 15 [ENDORSED]
Replies: 1
Views: 229

Re: Chapter 1 HW Question 15 [ENDORSED]

Oh that's because n2^2 is in the denominator and ~0.112=1/9. So basically 1/n2^2=1/9 basically means n2^2=9 and n2=sqrt(9)=3 :)
by Marie_Bae_3M
Fri Sep 30, 2016 2:25 pm
Forum: Photoelectric Effect
Topic: About photons.... [ENDORSED]
Replies: 3
Views: 388

About photons.... [ENDORSED]

Can increasing the amount of photons emit an electron or must the photons themselves need more energy to eject an electron? Thank you :)

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