### Fall 2010 Final Exam

Posted:

**Fri Dec 04, 2015 6:49 pm**For question 2A, the final answer is 6. But I don't understand how you get 6 from 1/(n^2) = 2.78 x 10^-2

Can someone explain how you get 6?

Can someone explain how you get 6?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=17&t=8949

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Posted: **Fri Dec 04, 2015 6:49 pm**

For question 2A, the final answer is 6. But I don't understand how you get 6 from 1/(n^2) = 2.78 x 10^-2

Can someone explain how you get 6?

Can someone explain how you get 6?

Posted: **Fri Dec 04, 2015 10:39 pm**

It looks like you have the previous steps correct (making ΔE or hv negative because light was emitted, using the right constants, etc.) and all you need to do is solve for n. Multiply both sides by n^{2}, so you will have 1 = (n^{2})(2.78x10^{-2}). Then divide both sides by 2.78x10^{-2} to get 1/(2.78x10^{-2})=n^{2}. Then take the square root of both sides to solve for n. The answer should be about 5.9976 which rounds to 6.