## 1B.7 b)

Labiba Sardar 2A
Posts: 103
Joined: Sat Jul 20, 2019 12:15 am

### 1B.7 b)

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?

Mariepahos4D
Posts: 50
Joined: Sat Sep 07, 2019 12:19 am

### Re: 1B.7 b)

It wants to know how much energy is emitted from that quantity of sodium atoms so the answer would be the total amount of energy emitted by all of the atoms not per individual answer so J/atom would be incorrect since you that is not the energy per each atom.