exam #2 results this week’s schedule lecture- lab- announcements
Post on 21-Dec-2015
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TRANSCRIPT
Energy is Quantized
Light also acts like particlesPhoton= “Packet” of energyEnergy is proportional to Frequency (and )Planck’s Equation:
hEphoton
Some more examples…
How much energy does a mole of 230nm photons possess?
Can this light break a C-C bond with an energy of 346kJ/mol?
c
chhEphoton
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For one photon :
E photon = h ⋅ν =h ⋅cλ=(6.626x10−34 J ⋅s)(3.0x108m /s)
230x10−9m= 8.64x10−19J
For one mole of photons :
E =8.64x10−19J
photon⋅6.02x1023 photons
1mole= 520285J = 520kJ
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520kJ > 346kJ , ∴ yes 230nm light CAN break a C −C bond.
Does 1 mole of 1200nm photons have enough energy to break a C-C bond?
1 2 3
62%
13%
26%
1. Yes2. No3. Abstain
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For one photon :
E photon = h ⋅ν =h ⋅cλ=(6.626x10−34 J ⋅s)(3.0x108m /s)
1200x10−9m=1.6x10−19J
For one mole of photons :
E =1.6x10−19J
photon⋅6.02x1023 photons
1mole= 99721J = 99.7kJ < 346kJ
Where does light come from?
Excited solids emit a continuous spectrum of light
Excited gas-phase atoms emit only specific wavelengths of light (“lines”)
Emission spectra of gaseous atoms
Excited atoms emit light of only certain wavelengths
The wavelengths of emitted light depend on the element.