Answer :
The difference in energy between the two levels responsible for the ultraviolet emission line of the magnesium atom at 202.5 nm is 419.4 kJ/mol
The energy of a photon may be calculated in ways: If the photon's frequency is known, we will use the formula E = h f . Max Planck proposed this equation, which is why it is called Planck's equation. If the photon's wavelength is known, the photon's energy may be calculated with the use of the system E = h c λ.
The frequency of a photon is described as how many wavelengths a photon propagates every second. in contrast to an electromagnetic wave, a photon cannot simply be of a coloration. instead, a photon will correspond to light of a given color.
calculation:-
Wavelength λ = 285.2 nm = 285.2 x 10-9 m
Energy difference ΔE = photon energy = hc/λ
= 6.626 x 10-34 x 2.998 x 108/285.2 x 10-9
= 6.965 x 10-19 J
where h is Planck constant and c is the speed of light
If you need the energy difference in kJ/mol, then multiply the above value by Avogadro's number:
ΔE(kJ/mol) = 6.965 x 10-19 x 6.022 x 1023
= 4.194 x 105 J/mol = 419.4 kJ/mol
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