[jjkwest1]

It takes light with a wavelength of 261 nm, or less, to break the O-H bond in water. What energy does this correspond to (in kJ/photon) and what is the O-H bond strength in kJ/mol?

What i did to find the energy of a photon was E= hc/λ  = (6.626*10^-34)(3*10^8)/(261/10^9) = 7.62*10^-19 j/photon

7.62*10^-19/1000= 7.63*10^-22 kJ/photon

So i found the energy of the photon but i don't know how to find the O-H bond strength.

[P]

Not sure as I've not done this for years, so don't take this as gospel,  but if you've found the energy required to break one bond, then can't you use Avogadro's number to find the energy required per mole?

[GollumsLunch]

The previous poster has it right.  You have calculated that the energy is 7.62e-19 J/photon.  You now just need to use that there are 6.022e23 photons/mole so

7.62e-19 J/photon * 6.022e23 photon/mole = 458000 J/mol

And converting to kJ/mol you get 458 kJ/mol.