How many kj/mol (of photons) of energy is contained in light with a wavelength of 4966.36nm?

For one particle
With h and plancs constant and c as the speed of light

E = h nu

E = h (c/lambda)

E = h (c/4966.39*10^-9m)

Then you multiply that by 6.02*10^23 to find the j/mol

Then you divide by 1000 for kj

We know, E = Planck's constant * speed of light  / wavelength

Here, h = 6.62607004 × 10-34 m2 kg / s
c = 3 * 10^8 m/s
w = 4966.36 nm = 4966.36 * 10^-9m = 4.96636 * 10^-6 m

Substitute their values, 
E = (6.62607004 × 10-34) (3 * 10^8) / (4.96636 * 10^-6)
E = 19.88 × 10^-26 / 4.96636 * 10^-6
E = 4 × 10^-20 J
E = 4 × 10^-20 / 10^3
E = 4 × 10^-23

In short, Your Answer would be: 4 × 10^-23 KJ

Hope this helps!