Page 1 of 1

### 1B.7

Posted: Sun Oct 14, 2018 10:02 pm
Sodium vapor lamps, used for public lighting, emit yellow light of wavelength 589nm. How much energy is emitted by 5.00 mg of sodium atom emitting this wavelength?

### Re: 1B.7

Posted: Mon Oct 15, 2018 11:08 am
Convert wavelength to energy by using the energy formula E=hν. Because νλ is equal to the speed of light this can be rewritten as E=hC/λ. You now have a formula that you can plug in values for and get the energy for one the emission of one atom (3.37 e-17).
Next, convert the mass of sodium into atoms by using the molar mass and Avogadro's number (5.00)(22.99)^-1(6.022e23)=1.31e23
Now multiply the number of atoms by the energy released from each atom (3.37e-17 J x 1.31e23) to get your final answer (4.41e6 J).

### Re: 1B.7

Posted: Tue Oct 16, 2018 12:14 pm
To find b, you have to first convert 5.00 mg Na to atoms.

5.00 mg Na x 1g/1000mg Na = 5.00 x 10^-3 g Na
5.00 x 10^-3 g Na x 1 mol/22.99 g Na x 6.022 x 10^23 atoms/1 mol ... = your answer

After you find the atoms, you have to multiply the atoms with the answer you got in part a (3.37 x 10^-19 J. atom^-1), which is the energy released from each atom. After multiplying it together, you should get 44.1 J as your answer!