1. What is the wavelength, in nanometers, of light with an energy content of 2.31E9 kJ/mol?

2. What is the maximum kinetic energy of an ejected electron if chromium metal is irradiated with 2.50E2-nm light? The threshold wavelength for a chromium metal surface is 276 nm. Use exponential notation (e.g. 1.23e-19).

3. What must be the velocity, in meters per second, of a beam of electrons if they are to display a de Broglie wavelength of 83.0 μm?

4. If the electron in a hydrogen atom undergoes a transition from an n = 5 level to an n = 1 level, what is the wavelength of the radiation emitted?

5. What is the shortest wavelength of light that can be emitted by a hydrogen atom that has an initial configuration of 4p1?

Just want to make sure I did these questions correctly. Thanks!

1)use this relation
E = h X c/ wavelength
wavelength=  E / hxc
h = 6.6 X 10^-34 J.s
c= 3 X 10^8 m/sec
E is given in KJ so convert it in J
wavelength will come in m
Use this conversion factor
1m = 10^ 9 nm

Kinetic energy of the ejected electron = absorbed energy - threshold energy
absorbed energy = hv = hc/wavelength
threshold energy = hc/ wavelength of ejected electron
you can now plug in the values to take out the kinetic energy

wavelength = h / mv
v (velocity of electron) = wavelength X mass of electron / h
plug in all values
1m = 10^6 um

q-4
energy of hydrogen atom = -1.312 X 10^6  Z^2/ n^2
for H  Z = 1
E1 =  -1.312 X 10^6 J/mol
E5 =  -1.312 X 10^6 / 25

deta E = E5-E1 = hc / wavelength

Shortest wavelength means maximum  energy
now  electron is in n=4
maximum energy will be emitted if electron jumps from highest to lowest (n=1) level
hence
delta E = E4 - E1 = h c / wavelength
I hope now you can try it