### 1B.7 b)

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**Sun Oct 13, 2019 10:59 am**Sodium vapor lamps emit yellow light of wavelength 589 nm. How much energy is emitted by b) 5.00mg of Na atoms emitting light at this wavelength?

From a) I found that the energy emitted by an excited sodium atom is 3.37 x 10^-19 J. Then for part b, I found that 5.00mg of Na atoms = 1.31 x 10^20 Na atoms. The solutions manual says that you have to multiply 3.37 x 10^-19 J (and they list the unit as J/atom) with 1.31 x 10^20 Na atoms to get Joules in your ending answer. How come you can't just do (3.37 x 10^-19 J) / (1.31 x 10^20 atoms) to get J/atom as your answer instead of multiplying it together and getting Joules as your answer?

From a) I found that the energy emitted by an excited sodium atom is 3.37 x 10^-19 J. Then for part b, I found that 5.00mg of Na atoms = 1.31 x 10^20 Na atoms. The solutions manual says that you have to multiply 3.37 x 10^-19 J (and they list the unit as J/atom) with 1.31 x 10^20 Na atoms to get Joules in your ending answer. How come you can't just do (3.37 x 10^-19 J) / (1.31 x 10^20 atoms) to get J/atom as your answer instead of multiplying it together and getting Joules as your answer?