Skip to main content
Ch.7 - Quantum-Mechanical Model of the Atom
Chapter 7, Problem 93

Assuming total absorption of the light by the sample, what is the maximum amount (in moles) of CH3X that breaks apart when a cuvette containing a solution of CH3X is irradiated with 280-nm light with a power of 885 mW for 10.0 minutes, given that the quantum yield for the reaction CH3X → CH3 + X is f = 0.24?

Verified step by step guidance
1
Calculate the energy of a single photon using the formula: \( E = \frac{hc}{\lambda} \), where \( h \) is Planck's constant (6.626 \times 10^{-34} \text{ J s}), \( c \) is the speed of light (3.00 \times 10^8 \text{ m/s}), and \( \lambda \) is the wavelength (280 \text{ nm} = 280 \times 10^{-9} \text{ m}).
Determine the total energy supplied by the light source using the formula: \( \text{Total Energy} = \text{Power} \times \text{Time} \), where the power is 885 mW (or 885 \times 10^{-3} \text{ W}) and the time is 10.0 minutes (or 600 seconds).
Calculate the total number of photons using the formula: \( \text{Number of Photons} = \frac{\text{Total Energy}}{E} \), where \( E \) is the energy of a single photon calculated in step 1.
Use the quantum yield (\( f = 0.24 \)) to find the number of moles of CH3X that dissociate. The formula is: \( \text{Moles of CH3X} = \frac{\text{Number of Photons} \times f}{N_A} \), where \( N_A \) is Avogadro's number (6.022 \times 10^{23} \text{ mol}^{-1}).
The result from step 4 gives the maximum amount of CH3X in moles that breaks apart under the given conditions.