# Photons, wavelengths, and ionization energy

1. Oct 18, 2005

### confusedbyphysics

This is a post-lab question for my chemistry lab but it is kind of physics too so I thought I'd post it here (the other sciences sections don't much response).. It's confusing because the questions are supposed to go along with what we are learning in the chemistry lecture, but we're behind in the lecture, so I'm trying to teach myself how to do this since we haven't learned it yet!

Here's the problem:

"The ionization energy of Li is 520 kJ/electron mole. What is the wavelength of nm of a photon having sufficient energy to remove an electron from Li? In what portion of the electromagnetic spectrum would you find such a photon?"

My work:

520 kJ = 520000 J

520000 J/mol X 1 mol / 6.02 X 10^23 photons = 8.6379 X 10^-19 J / photons

Energy = h (constant) X v (frequency)

v = E/h

v = (8.6379 X 10^-19 J/photons) / (6.626 X 10 ^-34 J/s)

v = 1.3036 X 10 15 /s

wavelength (w) = speed of light (c)/ v

w = (3 X 10^8 m/s) / (1.3036 X 10^15)

w = 2.301 m /photon X 10^9 nm/m = 230 nm

230 nm = ultraviolent rays

Does this look right? If someone could help me Id soooo appreciate it! (I need to make sure I did this right or I'll miss the next problem too because they're related)

2. Oct 18, 2005

### lightgrav

Looks good ... equations used correctly.
I didn't check your calculator punching,