Answer:
4.34x10⁻¹⁹ J
Explanation:
The total energy emitted by irradiation is given by
E = hf, where E is the energy, h is the plack constant (6.626x10⁻³⁴ J.s), and f is the frequency. The frequency is also the velocity of the light (c = 2.99x10⁸ m/s) divided by the length of the irradiation (254x10⁻⁹ m). So:
E = (6.626x10⁻³⁴)x(2.99x10⁸)/ (254x10⁻⁹)
E = 7.80x10⁻¹⁹ J
The energy to remove 1 electron is the energy necessary to remove 1 mol divided by the Avogadros number ( 1 mol = 6.02x10²³ electrons):
208400/6.022x10^23 = 3.46x10⁻¹⁹ J
The total energy is the energy necessary to remove one electrons plus the kinectic energy (Ek) of the electrons:
7.80x10⁻¹⁹ = 3.46x10⁻¹⁹ + Ek
Ek = 7.80x10⁻¹⁹ - 3.46x10⁻¹⁹
Ek = 4.34x10⁻¹⁹ J
