Question

Rose bengal is a chromophore used in biological staining that has an absorption maximum at 559.1 nm and several other shorter wavelength absorption bands in the ultraviolet and visible regions of the spectrum when dissolved in ethanol. What is the energy difference, in kilojoules per mole, between the absorption maximum at 559.1 nm and a band at 263.5nm?

Answer 1

-3.99 × 10⁻²² kJ/mol

Step-by-step explanation:

We can calculate the energy (E) of 1 mole of photons using the Planck-Einstein equation.

E = h × c × λ⁻¹

where,

h: Planck's constant

c: speed of light

λ: wavelength

E(559.1 nm) = (6.63 × 10⁻³⁴ J.s) × (3.00 × 10⁸ m/s) × (559.1 × 10⁻⁹m)⁻¹

E(559.1 nm) = 3.56 × 10⁻¹⁹ J = 3.56 × 10⁻²² kJ = 3.56 × 10⁻²² kJ/mol

E(263.5 nm) = (6.63 × 10⁻³⁴ J.s) × (3.00 × 10⁸ m/s) × (263.5 × 10⁻⁹m)⁻¹

E(263.5 nm) = 7.55 × 10⁻¹⁹ J = 7.55 × 10⁻²² kJ = 7.55 × 10⁻²² kJ/mol

E(559.1 nm) - E(263.5 nm) = 3.56 × 10⁻²² kJ/mol - 7.55 × 10⁻²² kJ/mol =

-3.99 × 10⁻²² kJ/mol