Ionisation energy of Hydrogen? (2 Viewers)

[IAU001]

hey i read this q in the dot point book and i have absolutely no clue how to do it =S

Use the Rydeberg equation to calculate the ionisation energy for hydrogen.


the answer iss 13.625 eV. how do we get that?

thanks in advance to anyone hu can help!

 

[Dumbledore]

use Ni = 1 and Nf = infinity, by definition the work required to move the electron from the inifinite(outside atom) state to the lowest state, this x -1 will become the ionisation energy

 

[cybob101]

i thought this was a joke lol. wat dumby said

 

[IAU001]

yeah i tried that but i dont seem to be getting the right answer

ok yer im clearly a dumbass man dont need to rub it in =P

but yeah i thoguht of that, and u end up getting 1/lamda = R x 1

which dusnt give me 13.6 eV wen i convert it from joules.=S

 

[darkchild69]

yeah i tried that but i dont seem to be getting the right answer

ok yer im clearly a dumbass man dont need to rub it in =P

but yeah i thoguht of that, and u end up getting 1/lamda = R x 1

which dusnt give me 13.6 eV wen i convert it from joules.=S

Mate, you must be doing it wrong. How dumble said to do it is kinda correct, just missing a step.

Use Rydberg's equation, ni=1, nf= infinity

Comes out to be 13.6eV

It sounds like you are finding the wavelength and then dividing the wavelength by 1.602x10^-19J

You are missing a step mate.

These are the steps to follow:

1. You need to find the wavelength (using rydberg-balmer eqn)

2. Substitute this into E=hc/lambda (to find energy in Joules)

3. Convert this to eV (dividing by 1.602x10^-19)



I actually put this question in my schools trial

 

[Aerath]

Just thought I'd point out that the answer to this in Joules in DP is incorrect. It's out by a factor of 10.

 

[darkchild69]

Just thought I'd point out that the answer to this in Joules in DP is incorrect. It's out by a factor of 10.

Just add it to the list!

Damn Shadwick and his errors!

 

[Aerath]

Actually, it's not him writing the answers apparently. Apparently he palms that (boring) responsibility off to one of his students.

 

[High_Pride]

Sorry if this is a, err, "stupid" question, but don't you get a negative if you let nf = infinity and ni=1?

 

[themass1]

Darkchild
Is right I was just doing the same question and I was trying to igure out the answer
Straight from the wavelength nt known you had to sub into the e=hf which makes total sense:s because that's wat the question is acuLly asking