When a compound containing cesium ion is heated in a Bunsen burner flame, photons with an energy of 4.30 x 10-19 J are emitted. What color is the cesium flame?

Answer 1

Lauren,

The wavelength will help to tell you the color of the flame.

use the equation E = h*c/λ to calculate the wavelength

E = energy ( given in the question as 4.30 x 10^-19J)

h = Planck’s Constant (6,626 x 10^-34J s)

c = speed of light ( 3.00 x 10⁸ m/s)

λ = wavelength

Rearranging the equation we get λ = h*c/E

so λ = (6.626 x 10^-34J s) x (3.00 x 10⁸ m/s) divided by 4.30 x 10^-19J

All units will cancel leaving you with an answer in m (meters) …..4.62 x 10^-7 m

convert this to nm since that’s usually the wavelength unit associated with color (in the visible region)

1 m = 1 x 10⁹ nm, so 4.62 x 10^-7 m x (1 x 10⁹ nm)/1m = 462 nm

Check the visible region of the electromagnetic spectrum and you will see that this wavelength falls in the blue region with respect to colour.