Calculate the longest wavelength of light (nm)that can be used to remove electrons from metal surfaces if 245 kJ/mol is required to eject electrons.
A)233
B)488
C)725
D)552
E)165

Question

Quizplus · Accepted Answer

The energy required to eject electrons is given in kJ/mol, so first, we convert this energy to Joules per electron. Since 1 mol = 6.022 x 10^23 particles (Avogadro's number), 245 kJ/mol = 245,000 J/mol. Therefore, the energy per electron is 245,000 J / (6.022 x 10^23) = 4.07 x 10^-19 J/electron. The energy of a photon (E) is given by E = hc/λ, where h is Planck's constant (6.626 x 10^-34 m^2 kg / s), c is the speed of light (3.00 x 10^8 m/s), and λ is the wavelength in meters. Rearranging for λ gives λ = hc/E. Substituting the values gives λ = (6.626 x 10^-34 * 3.00 x 10^8) / 4.07 x 10^-19 = 4.88 x 10^-7 meters, or 488 nm.

Calculate the Longest Wavelength of Light (Nm)that Can Be Used