CHEMISTRY COMMUNITY

Marie_Bae_3M

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.

Marie_Bae_3M

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...

Marie_Bae_3M

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...

Marie_Bae_3M

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...

Marie_Bae_3M

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]...

Marie_Bae_3M

I'd love to!! How does Monday night sound to you? :)

Marie_Bae_3M

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

Marie_Bae_3M

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...

Marie_Bae_3M

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...

Marie_Bae_3M

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.

Marie_Bae_3M

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...

Marie_Bae_3M

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...

Marie_Bae_3M

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!

Marie_Bae_3M

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...

Marie_Bae_3M

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?

Marie_Bae_3M

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 ([])?

Marie_Bae_3M

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?

Marie_Bae_3M

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. :)

Marie_Bae_3M

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...

Marie_Bae_3M

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...

Marie_Bae_3M

Yes, I believe they mean the same thing :)

Marie_Bae_3M

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!!

Marie_Bae_3M

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 :)

Marie_Bae_3M

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 :)

Marie_Bae_3M

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

CHEMISTRY COMMUNITY

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Re: Midterm 2013 Q4A

Relationship between activation energy and pseudo delta g

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Re: Study Group for Midterm Winter 2017

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Calorimeters

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Equil. Constants and Temperature

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About photons.... [ENDORSED]