Posted by ssss on Thursday, May 30, 2013 at 6:37pm.
i guess this is one of the eDX CH3.091 final exam question???
Good guess :D
Good guess, that's why we need to help each other
ok..how about i do the talking and you do the calculations??..hope this is a best way we help each other, by working together, not just by giving the answer so that others can just jump in and take it without knowing its derivatives..its better to have postings leading to answers...
ok, the question ask for the N-N bond. so we need to rearrange the Bond Energy equation BE(NCl) = sqrt[BE(N-N) x BE (Cl-Cl)] + 96.3[X(N)-X(Cl)^2
rearrange the equation to make BE(N-N) the subject.
then we can use the de Broglie equation to find the wavelength..
can anyone try that??...i have 1 more submission left for this question..
what is v value in de Broglie's equation ??
But what is X(N) and X(Cl)?
v is the velocity which can be derived from E=1/2mv^2 (kinetic energy).
the X(N) is the electronegativity for Nitrogen and so as Cl obtained from the periodic table.
Answer plz...
still the answer is wrong..............
as bonjo said, let's try to do together
- rearrange the equation to make BE(N-N) the subject.
BE(NCl) - 96.3[X(N)-X(Cl)]^2 = sqrt[BE(N-N) x BE (Cl-Cl)]
BE(NCl) - 96.3[X(N)-X(Cl)]^2 = sqrt[BE(N-N) x BE (Cl-Cl)]
(BE(NCl) - 96.3[X(N)-X(Cl)]^2) / sqrt [BE (Cl-Cl)] = sqrt[BE(N-N)]
- Ok, let's put numbers now
(190 kJ/mol - 96.3 [3.04-3.16]) / sqrt [240 kJ/mol]= sqrt[BE(N-N)]
(ps. I used Pauling electronegativity values)
190 - 96.3(-0.12)/15.49 = sqrt[BE(N-N)]
(190 - 96.42) / 15.49 = sqrt[BE(N-N)]
93.58 / 15.49 = sqrt[BE(N-N)]
6.04 = sqrt[BE(N-N)]
(6.04)^2 = (sqrt[BE(N-N)])^2
36.49 = [BE(N-N)]
what's missing??
the velocity of the electron is sqrt(2E/m) where E is the bond energy for NN and m is the mass of electron.
So, v = sqrt (2 x 36.49 / 0.000548597 amu)
v = 72.98/0.000548597
v= 133030.25
now, we use the de Broglie equation to find the wavelength.
Broglie equation: w = h / m v, where w = wavelength; h = Planck's constant in J/s; m = mass in kg; v = speed in m/s.
w = what we want to know
h = 6.63 x 10^-34 J s
m = 9.1 x 10^-31 kg (mass of an electron?)
v = I think that I calculete not im m/s
People, I don't know if I'm in the right way... Could someone HELP too??
marcia, maybe you used kJ instead of j?
and...as the internet says, the bond energy for the N-N bond is about 170kj/mol.
Solution: 9.8e-10 meter
Deatils:
- Calculated N-N bond energy: 150.4kJ/mol = 2.507e-19J/molecule.
- v electron speed: 7.42e5 m/s
- de Borglie wave lenght = h / (m x v), where h Planc constant, m electron mass, v electron speed
Thanks a lot, Pahu!