Asked Nov 11, 2019

The bright-red color of highway safety flares comes from strontium ions in salts such as Sr(NO3)2 and SrCO3. Burning a flare produces strontium ions in excited states, which then emit red photons at 606 nm and several wavelengths between 636 and 688 nm. Calculate the energy (in Joules per mole) of the 683 nm emission.


Expert Answer

Step 1

The relationship between wavelength and energy is given as:


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h c E Where, E energy of one photon (J h Planck's constant 6.626 x 10-34 J s c speed of light 3 x 108 m/s = wavelength (m)

Step 2


Wavelength = 683 nm = 683 × 10-9 m     (1 nm = 10-9 m)

The energy can be calculated as:


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h c E λ 6.626 х 10 34 ] sx3X108 m/s Е- 683 х 10-9 m E 2.91 x 10-19 J

Step 3

The value of energy in Joules per ...


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Energy 2.91 x 10-19 J x Avogadro's number Energy 2.91x 10-19 J x 6.022 x 1023 mol1 Energy 175240.2 J/mol


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