An x-ray photon of wavelength 0.989 nm strikes a surface. The emitted electron has a kinetic energy of 969 eV. What is the binding energy of the electron in KJ/mol?
KE = hv - ϕ; hv - KE = ϕ;
c/lambda = v; 3*108 / (.989 / 109) = v = 3.03 * 1017 s-1
hv - KE = ϕ;
(6.626 * 10-34 Js)(3.03 * 1017 s-1) - 969 eV = ϕ
2.007678*10-16 J - 969 eV = ϕ
convert electron volts to joules:
969 eV * ((1.602 * 10-19)J/1eV) = 1.552338 * 10-16 J
2.007678*10-16 J - 1.552338 * 10-16 J = ϕ
ϕ = 4.5534 * 10-17 J
Now convert to KJ/mol: I don't know where to go from here, do I use avogadro's number?
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I think so.
You are watching: What is the binding energy of the electron in kj/mol?
Everything up to that point is for one electron? If you agree, then yes, use Avogadro's number to get to moles.
Op · 5y
What should that look like, do I divide by avogadros number? I guess I don't understand why you would want the binding energy in mols of electrons. I also don't have an answer key or an example for this problem so I feel naked about it.
Convert to KJ:
4.5534 * 10-17 J / 1000 J = 4.5534 * 10-20 KJ
Divide by avogadros number to get KJ per mole?:
4.5534 * 10-20 KJ / 6.022 * 1023 = 7.56127532 * 10-44 KJ/mol = ϕ?
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Avogadro's number is in units of mol-1, so multiplying by it will take care of that. Then you divide by 1000 to go from J to kJ. 90% of the way there already. Well done.
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