In: Chemistry
Determine the energy of 1.40 mol of photons for each of the following kinds of light. (Assume three significant figures.)
A. infrared radiation (1430 nm )
B. ultraviolet radiation (135 nm )
We can always relate Wavlenegth and Energy per photon via:
Therefore, get first, Energy per photon, then per mol of photon:
E = h c / WL
h = Planck Constant = 6.626*10^-34 J s
c = speed of particle (i.e. light) = 3*10^8 m/s
W = wavelenght in (m) change from nanometers by 10^-9 ratio
E = energy per particle J/photon
Now, calcualte
a)
E = hc/WL
E = (6.626*10^-34)(3*10^8)/(1430*10^-9) = 1.390*10^-19 J/photon
we have, 1.4 mol of photon, or
photons = 1.4*6.022*10^23 = 8.4308*10^23 photons
Etotal = Eper photon * no of photons = 1.390*10^-19 J/photon * 8.4308*10^23 photons
Etotal = ( 1.390*10^-19)( 8.4308*10^23 ) = 117188.12 J = 117.188 kJ --> 3 sig fig --> 1.17*10^2 kJ
b)
similarly:
E = hc/WL
E = (6.626*10^-34)(3*10^8)/(135*10^-9) = 1.47244*10^-18 J/photon
we have, 1.4 mol of photon, or
photons = 1.4*6.022*10^23 = 8.4308*10^23 photons
Etotal = Eper photon * no of photons = 1.47244*10^-18 J/photon * 8.4308*10^23 photons
Etotal = ( 1.47244*10^-18)( 8.4308*10^23 ) = 1241384.7152 J = 1241.38 kJ --> 3 sig fig --> 1.24*10^3 kJ