In: Chemistry
What is the wavelength in meters of 91.0 kJ/mol
Ans- 1 mole *(6.02 x 1023) of
photons have 91.0 kJ/mol of energy,so the energy of a single
photon. 91.0 kilojoules to joules by multiplying by 1,000. This
equals 91000 joules. Next, divide this number by 6.02 x
1023 photons to find the energy in a single
photon:
(9.1 x 104 J) / (6.02 x 1023 photons) = 1.51
x 10-19 J/photon
The formula for the energy of a photon is
energy = Planck's constant x frequency
Unfortunately, it does not contain the wavelength so we need
enother equation:
speed of light = frequency x wavelength
frequency = speed of light / wavelength
Substituting for frequency in the top equation, we get:
energy = (Planck's constant x speed of light) / wavelength
wavelength x energy = Planck's constant x speed of light
wavelength = (Planck's constant x speed of light) / energy
The speed of light in a vacuum is a universal constant equal to 3 x
108 m/s. Plack's constant is given as 6.63 ×
10−34 J∙s . Substituting in the above equation we
get:
wavelength = [(6.63 × 10−34 J∙s)(3x 108 m/s)]
/ (1.51 x 10-19 J) = 1.31 x 10-6 m.
The wavelength of photons with the energy of 91.0 kJ/mol is 1.31 x
10-6 meter.