Can Anyone Check My Chemistry HW?

Question

Q.) In a future hydrogen-fuel economy, the cheapest source of H2 will certainly be water. it takes 467kJ to produce 1 mol of H atoms from water. what is the frequency, wavelength, and minimum energy of a photon that can free an H atom from water?

V=E/h-->> { (467kJ)(10^3J/1KJ) (mol/6.022x10^23) / (6.626x10^-34) }
E=7.75x10^-19
V=1.17x10^15

Lamda=hc/E-->> { (6.626x10^-34J) (3.00x10^8) / (7.75x10^-19) }
Lamda=2.56x10^-7

So is this right?

Answer 1

I have checked your answers and they are all correct.
You should include the units.
Your energy of the photon is in joules. It is more common to quote this in electron volts.
You should also note that this is a minimum frequency and a maximum wavelength

467Kj/mole = 467000/6.022x10~23 = 7.755x10-19J/atom

As E=Hf , min f = E/h = 7.755x10-19/6.626x10-34 = 1.170x10~15s-1
v=fw so max w =v/f =3x10~8/1.170/10~15 =2.56x10-7m

Answer 2

Your equations are correct and your math looks good, but you should follow the units better.

256 nm may be a little high for the wavelength. Recent research seems to support 243 nm or 117.59 Kcal/mol.

See the reference below:

Answer 3

yeah, that's right.