Honors Chemistry I
Electromagnetic Spectrum Problems
Constants to know:
c = 3.00 x 108 m/sec;
h = 6.63 x 10-34 Joule-sec
Formulas: c =  ;
E = h
Units to remember:
1 meter = 1010 Angstrom = 1012 pm
= 109 nm
E = hc/
Units of frequency are in /sec or sec-1 which means there is no unit in the numerator. Frequency is
defined as the number of waves/sec.
1.
What is the frequency of light if it known to have a wavelength of 455 nm?
455 nm = 4.55 x 10-7 m
3.00 x 108 = (4.55 x 10-7)()  = 6.59 x 1014 s-1
2A. What is the wavelength of light (in nm) if it has a frequency of 2.33 x 1017 /sec?
3.00 x 108 = ()(2.33 x 1014)
 = 1.29 x 10-9 m = 1.29 nm
2B. What is this wavelength in Angstroms (A)? in picometers (pm)?
1.29 nm = 12.9 Å = 1290 pm
2C. From the chart given, determine what type of electromagnetic radiation it is?
Xray
3.
How much energy is released when an electron drops to the ground state and releases light with a
frequency of 5.00 x 1015 sec-1 ?
E = (6.636 x 10-34)(5.00 x 1015)
4.
E = 3.32 x 10-18 J
How much energy (in kJ) is released when one mole of the same type of electron drops back to the
ground state?
3.32 x 10-18 J/photon x (6.022 x 1023 / 1 mol) = 2.00 x 106 J/mol = 2.00 x 103 kJ/mol
5.
How much energy (in Joules) is released when an electron releases a photon that has a wavelength of
333 Angstroms?
333 Å = 3.33 x 10-8 m
6.
E = (6.636 x 10-34)(3.00 x 108)/3.33 x 10-8 = 5.98 x 10-18 J
If an electron releases one photon with an energy of 3.96 x 10-13 Joules, what is the wavelength (in cm)
of that wave?
3.96 x 10-13 J = (6.636 x 10-34)(3.00 x 108)/ 
7.
 = 5.03 x 10-13 m = 5.03 x 10-11 cm
If 2.23 moles of photons emit a total of 34.5 kJ of radiant energy, what would be the wavelength (in
Angstroms) of a single photon?
34.5 kJ/2.23 mol = 15.5 kJ/mol = 15500 J/mol x (1 mol / 6.022 x 1023) = 2.57 x 10-20 J / photon
2.57 x 10-20 = (6.636 x 10-34)(3.00 x 108)/
8.
 = 7.75 x 10-6 m = 7.75 x 104 Å
What is the energy of the fourth shell? Need to use the Rydberg equation.
En = 2.18 x 10-18 J(1/42) = -1.36 x 10-19 J
9. What is the energy of a photon that is released when an electron drops from the fourth to the third shell?
ΔE = 2.18 x 10-18 (1/42 – 1/32) = -1.06 x 10-19 J
10. What type of EM radiation is associated with the photon released in #9?
1.06 x 10-19 = (6.636 x 10-34)(3.00 x 108)/  = 1.88 x 10-6 m
infrared