Chemiluminescence occurs when a chemical reaction produces light. For instance,

Question

Chemiluminescence occurs when a chemical reaction produces light. For instance, the reaction of luminol (C8H7N3O2) with hydrogen peroxide (H2O2) produces a vibrant blue color (=470nm). The chemical equation of the luminol reaction is C8H7N3O2+H2O-->Product + photon

a. What ist the energy of a photon emitted by a single luminol molecule during this reaction

b. Based on your answer in a, how much energy does the luminol reaction produce per mole

c. Suppose you react 1 g of luminol and 1 g of hydrogen perxoide, How many photons will be produced

d. How much total energy is released during the chemiluminesece reaction in part c

Explanation / Answer

a)

E = hc/WL

h = Planck Constant = 6.626*10^-34 J s

c = speed of particle (i.e. light) = 3*10^8 m/s

E = energy per particle J/photon

E = (6.626*10^-34 )(3*10^8)/(470*10^-9) = 4.229*10^-19 J/photon

b)

energy per mol

1 mol = 6.022*10^23

4.229*10^-19 J/photon * (6.022*10^23 photons) / photon = 254670.38 J/mol

c)

1 g of luminol and 1g of H2O2...

MW of luminol = 177.16 g/mol

MW of peroxide = 34 g/mol

limiting reactant will be luminol

mol of luminol = mass/MW = 1/177.16 = 0.0056446 mol of luminol

1 molecule = 1 photon

1 mol = 1 mol of photon

0.0056446 mol of luminol = 0.0056446 mol of photon

total photon = 0.0056446 *6.022*10^23 = 3.39*10^21 photons

d)

Etotal in chemiluminesence

E = E per mol * mol of photons

Etotal = 0.0056446 *254670.38 = 1437.51242 J

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