The Foundations of Chemistry

Exercises 233

122.When compounds of barium are heated in a flame, green
light of wavelength 554 nm is emitted. How much energy
is lost when one mole of barium atoms each emit one
photon of this wavelength?
123.A 60-watt light bulb consumes energy at the rate of 60
J s
^1. Much of the light is emitted in the infrared region,

and less than 5% of the energy appears as visible light.

Calculate the number of visible photons emitted per sec-

ond. Make the simplifying assumptions that 5.0% of the

light is visible and that all visible light has a wavelength

of 550 nm (yellow-green).