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May 27, 2015

May 27, 2015

Posted by **ssss** on Thursday, May 30, 2013 at 6:37pm.

Express your answer in m.

- chemistry -
**bonjo**, Thursday, May 30, 2013 at 9:47pmi guess this is one of the eDX CH3.091 final exam question???

- chemistry -
**Sena**, Friday, May 31, 2013 at 4:25pmGood guess :D

- chemistry -
**Josh**, Friday, May 31, 2013 at 4:50pmGood guess, thats why we need to help each other

- chemistry -
**bonjo**, Friday, May 31, 2013 at 9:06pmok..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..

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**Anony mous**, Saturday, June 1, 2013 at 2:16amwhat is v value in de Broglie's equation ??

- chemistry -
**Anonymous**, Saturday, June 1, 2013 at 4:19pmBut what is X(N) and X(Cl)?

- chemistry -
**bonjo**, Saturday, June 1, 2013 at 6:28pmv 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.

- chemistry -
**Anonyms**, Saturday, June 1, 2013 at 11:16pmAnswer plz...

- chemistry -
**nonu**, Sunday, June 2, 2013 at 4:34amstill the answer is wrong..............

- chemistry -
**marcia**, Sunday, June 2, 2013 at 5:23pmas 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??

- chemistry -
**marcia**, Sunday, June 2, 2013 at 9:17pmthe 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

- chemistry -
**marcia**, Sunday, June 2, 2013 at 9:21pmnow, 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.

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**marcia**, Sunday, June 2, 2013 at 9:27pmw = 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

- chemistry -
**marcia**, Sunday, June 2, 2013 at 9:28pmPeople, I don't know if I'm in the right way... Could someone HELP too??

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**Anonymous**, Monday, June 3, 2013 at 2:18ammarcia, maybe you used kJ instead of j?

- chemistry -
**Anonymous**, Monday, June 3, 2013 at 2:19amand...as the internet says, the bond energy for the N-N bond is about 170kj/mol.

- chemistry -
**Pahu**, Monday, June 3, 2013 at 6:35amSolution: 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

- chemistry -
**Anonymous**, Monday, June 3, 2013 at 7:00amThanks a lot, Pahu!