ionisation energy

[Ice-cream]

hey guys, ive got this question which i know it should be pretty straight forward but for some reason, i cant get the answer:

 

Calculate the ionisation energy in kJ for a mole of hydrogen atomst that are in the n=2 energy level.

 

I think i just use E = -2.18e-18 Ze2 (1/nfinal - 1/ninitial)

 

what i did was substitute 1 for Z, infiinity for n final, so that becomes zero, then n = 2 into n initial. my answer ended up being 5.45e-19J, which is way too small for the answer...the answer provided was 328kJ.

 

can any1 point out what im doing wrong?

 

thanx

[swansont]

hey guys' date=' ive got this question which i know it should be pretty straight forward but for some reason, i cant get the answer:

 

Calculate the ionisation energy in kJ for [b']a mole[/b] of hydrogen atomst that are in the n=2 energy level.

 

I think i just use E = -2.18e-18 Ze2 (1/nfinal - 1/ninitial)

 

what i did was substitute 1 for Z, infiinity for n final, so that becomes zero, then n = 2 into n initial. my answer ended up being 5.45e-19J, which is way too small for the answer...the answer provided was 328kJ.

 

can any1 point out what im doing wrong?

 

thanx

 

You solved for one atom. Is that what the question was asking for? (Emphasis added, hint, hint)

[Ice-cream]

wow! thanks heaps! i can't believe i didn't see that, no wonder i was getting all these similar Q wrong!