## homework 1.25 part b

Husnia Safi - 1K
Posts: 33
Joined: Fri Sep 29, 2017 7:04 am

### homework 1.25 part b

sodium vapor lamps emit yellow light wavelength 589 nm. How much energy is emitted by 5.00 mg of sodium atoms emitting light at this wavelength

The solution to this problem says to convert 5 mg of Na to moles, then use that number and convert to Joules. But how would I know to do this by reading the problem?

Sunjum Singh 1I
Posts: 30
Joined: Fri Apr 06, 2018 11:05 am

### Re: homework 1.25 part b

You're actually changing the number into mols in order to multiply by Avogadro's number and get the atoms of Na which you use in your equation to find the energy of the sodium atoms.

Sarah Brecher 1I
Posts: 31
Joined: Fri Apr 06, 2018 11:02 am

### Re: homework 1.25 part b

In order to solve problems and get the correct answer, you need to make sure you start with the correct units. Since they're asking for energy, you would need to be in atoms. Mg isn't the correct unit and therefore you would need to convert from mg to g to mol to atoms using dimensional analysis.

Faisal Alshamaa - 1L
Posts: 31
Joined: Fri Apr 06, 2018 11:01 am

### Re: homework 1.25 part b

Since you know that the photoelectric effect, as well as in general, that all photon-electron interactions are one-to-one. So, you have to ask yourself how do I determine how many atoms of Sodium are in 5mg, and that is when you use the atomic mass to find the moles, and then from moles you multiply that by avogadros constant to determine the number of atoms in 5mg. You can then solve the problem. It's like a puzzle! Fun!