Determine the energy of 2.00 mol of photons for each kind of light. (Assume three significant figures.)

Question

Determine the energy of 2.00 mol of photons for each kind of light. (Assume three significant figures.)

Part (a) 1540 nm to kJ

Part (b) 520 nm to kJ

Paart (c) 140 nm to kJ

Answer 1

I answered this previously. Let's try it again.

E = hC/λ

E = energy of single photon

h = planck's constant = 6.626x10-34 Jsec

C = speed of light ~ 3x108 m/sec

λ = wavelength in meters

(a) E = (6.626x10^-34 Jsec)(3x10⁸ m/sec) / (1540x10^-9 m) = 1.29x10^-19 J / photon

1.29x10^-19 J/photon x 6.02x10²³ photons/mol x 2 moles = 1.55x10⁵ J x 1 kJ/10³ J = 155 kJ

(b) E = (6.626x10^-34 Jsec)(3x10⁸ m/sec) / (520x10^-9 m) = 3.82x10^-19 J/photon

3.82x10^-19 J/photon x 6.02x10²³ photons/mol x 2 mol = 4.60x10⁵ J x 1 kJ/10³ J = 460 kJ

(c) E = (6.626x10^-34 Jsec)(3x10⁸ m/sec) / 140x10^-9 m) = 1.42x10^-18 J/photon

1.42x10^-18 J/photon x 6.02x10²³ photons/mol x 2 mol = 1.71x10⁶ J x 1 kJ/10³ J = 1710 kJ

Does this make sense?