If DeltaH for the reaction I2 (s) Delta 2I (g) is 153 kJ/mol. What is the longest wavelength of light that can break an I – I bond? In other words, what is the minimum energy, expressed in terms of wavelength, required to break one I – I bond?
To determine the minimum energy required to break one I-I bond, we can make use of the relationship between energy and wavelength given by the equation:
E = hc/λ
Where:
E is the energy of the light
h is the Planck's constant (6.62607015 x 10^-34 J s)
c is the speed of light (2.998 x 10^8 m/s)
λ is the wavelength of the light
In this case, we want to find the longest wavelength of light that can break an I-I bond, which corresponds to the lowest energy. We can calculate this by rearranging the equation:
λ = hc/E
Now we know that ΔH = 153 kJ/mol represents the energy change accompanying the breaking of one mole of I-I bonds. To convert the energy change to joules per bond, we'll divide it by Avogadro's number (6.022 x 10^23 mol^-1):
Energy per bond (E) = ΔH / (Avogadro's number)
Now, we can substitute this value of E into the equation to calculate the longest wavelength (λ) that can break an I-I bond:
λ = (h * c) / E
Let's plug in the values and calculate:
Energy per bond (E):
E = (153 kJ/mol) / (6.022 x 10^23 mol^-1)
λ = (6.62607015 x 10^-34 J s * 2.998 x 10^8 m/s) / E
Calculate E and substitute it back into the equation for λ. After performing the necessary calculations, you will obtain the value for the longest wavelength.