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Postby ConnorRazmaDis2I » 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?

Jim Brown 14B Lec1
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Re: 1B.7

Postby Jim Brown 14B Lec1 » 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).

Grace Kim 1J
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Re: 1B.7

Postby Grace Kim 1J » 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!

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