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Home Q & A Board Science-Related Homework Help Physics
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jtshnnon jtshnnon
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11 years ago
The energy required to dislodge electrons from sodium metal via the photoelectric effect is 275 kj/mol. What wavelength in nm of light sufficient energy per photon to dislodge an electron from the surface of soidium?
How do you solve this? The book showed a diff example but not how to solve this one.
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#1
11 years ago
Planck?s equation will help:
E = hf = hc / ?
? = hc / E

where:
h = 6.626 E-34 J/s
f = frequency; c = speed of light = 3 E8 m/s; ? = wavelength

Now:
E = 275 kj/mol = 275,000 / 6.023 E23 J/atom
(Note: 6.023 E23 = # atoms in a mole = Avagadro number)
E = 2.75 E5 / 6.023 E23
E = 0.457 E-18
E = 4.57 E-19 J

Now:
? = hc / E = 6.626 E-34 x 3 E8 / 4.57 E-19
? = 4.35 E-7
? = 435 E-9 m
Answer = 435 nm
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