When 2.00 mol of H2(g) forms in the following reaction, ΔH = 572 kJ. 2 H2O(l) → 2 H2(g) + O2(g) What is the maximum wavelength of light (in nm) that can convert H2O into H2(g)?

Answer 1

E = hc/λ

E = energy = 572 kJ / 2 mol H₂ = 286 kJ/mol = 286,000 J/mol

h = Planks constant = 6.626x10^-34 J-s

c = speed of light = 3x10⁸ m/s

λ = wavelength in meters = ?

Solving for λ...

λ = hc/E = 6.626x10^-34 J-s (3x10⁸ m/s) / 286x10³ J

λ = 6.95x10^-31 m x 1 nm / 1x10^-9 m = 6.95x10^-22 nm (check the math)