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December 21, 2014

December 21, 2014

Posted by **Rossi** on Saturday, October 21, 2006 at 9:43am.

Ok, I know I have to find how many kJ will be needed to remove one electron. Do I find this number by dividing 208.4kJ by 6.022 x 10^23? I have been doing it that way and I get the wrong answer. How do I find how many kJ will be needed to remove ONE electron?

Once I find the energy, I divide hc by the energy, to get lambda, right?

The is the right approach. You dont want kJ, however, you want it in Joules.

Then, use Energy=Plancksconst*speedlight/lambda

solve for lambda. You have it correct, but watch for the correct units.

Well, this is what I have done:

208.4 kJ/ 1 mol x 1 mol/ 6.0221x10^23 = 3.461x10^-22 kJ = 3.461x10^-19 J

therefore,

6.626x10^-34 x 2.9979x106^8 / 3.461x10^-19 = 5.740x10^-7m = 574.0 nm (final answer)

This is an online homework problem, and each time I submit that answer it tells me I am wrong... that is why I believe I am not doing this problem correctly. Is there an error I am making?

I dont get

I've tried with rounding to the correct sig figs throughout the problem and then not rounding to the correct sig figs until the end, and no matter what form I put, it tells me I am wrong. This is stressing... thank you though

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