Question

1. If 0.500 mole of photons with a wavelength of 200.0 nm have an energy equal to  302 kJ, what is the energy of 0.500 mole of photons with a wavelength of 400.0 nm?

Answer 1

Given

wavelength 400 nm

400 nm = 400 × 10^-9 m

We need to find frequency ( v)

Frequency = Velocity of light/wavelength

v = c/​

v = 3 × 10⁸ms^-1/ 400 ×10^-9 m = 0.75 ×10^-15 s ^-1

^{Enerrgy of one photon E = hv}

h = 6.626 × 10^-34 Js = Planck's constant

^{putting value} E = 6.626 ×10^-34J s × 0.75 × 10¹⁵ s-1

E = 4.9695 × 10 ^-19 J

Energy of 0.500 mole photon

= 4.9695 × 10^-19 × 0.500 × 6.022 × 10²³

= 4.9695 × 3.011 × 10⁴

= 14.96 × 10⁴ J / mol

=149.6 × 10³ J / mol

= 149.6 kJ / mol