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Ch.6 - Electronic Structure of Atoms
Chapter 6, Problem 30

The energy from radiation can be used to cause the rupture of chemical bonds. A minimum energy of 242 kJ/mol is required to break the chlorine–chlorine bond in Cl2. What is the longest wavelength of radiation that possesses the necessary energy to break the bond? What type of electromagnetic radiation is this?

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1
Convert the energy required to break the bond from kJ/mol to J/molecule. Use the conversion factor: 1 kJ = 1000 J and Avogadro's number (6.022 x 10^23 molecules/mol).
Use the equation E = h\nu to relate energy (E) to frequency (\nu), where h is Planck's constant (6.626 x 10^-34 J·s). Rearrange the equation to solve for frequency: \nu = E/h.
Use the speed of light equation c = \lambda\nu, where c is the speed of light (3.00 x 10^8 m/s) and \lambda is the wavelength. Rearrange to solve for wavelength: \lambda = c/\nu.
Substitute the frequency calculated in step 2 into the equation from step 3 to find the wavelength.
Determine the type of electromagnetic radiation by comparing the calculated wavelength to the electromagnetic spectrum ranges.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Energy and Wavelength Relationship

The energy of electromagnetic radiation is inversely related to its wavelength, described by the equation E = hc/λ, where E is energy, h is Planck's constant, c is the speed of light, and λ is the wavelength. This means that as the wavelength increases, the energy decreases. Understanding this relationship is crucial for determining the longest wavelength that can still provide sufficient energy to break a chemical bond.
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Frequency-Wavelength Relationship

Bond Dissociation Energy

Bond dissociation energy is the amount of energy required to break a specific chemical bond in a molecule, measured in kJ/mol. In this case, the chlorine–chlorine bond in Cl2 requires 242 kJ/mol to break. This concept is essential for calculating the energy needed from radiation to achieve bond rupture.
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Types of Electromagnetic Radiation

Electromagnetic radiation encompasses a range of wavelengths and frequencies, including radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. The type of radiation that can break chemical bonds typically falls within the ultraviolet or higher energy regions, as these wavelengths possess sufficient energy to overcome bond dissociation energies.
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Related Practice
Textbook Question

An AM radio station broadcasts at 1010 kHz, and its FM partner broadcasts at 98.3 MHz. Calculate and compare the energy of the photons emitted by these two radio stations.

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Textbook Question

One type of sunburn occurs on exposure to UV light of wavelength in the vicinity of 325 nm. (c) How many photons are in a 1.00 mJ burst of this radiation?

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Textbook Question

One type of sunburn occurs on exposure to UV light of wavelength in the vicinity of 325 nm. (d) These UV photons can break chemical bonds in your skin to cause sunburn—a form of radiation damage. If the 325-nm radiation provides exactly the energy to break an average chemical bond in the skin, estimate the average energy of these bonds in kJ>mol.

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Textbook Question

A diode laser emits at a wavelength of 987 nm. (a) In what portion of the electromagnetic spectrum is this radiation found? (b) All of its output energy is absorbed in a detector that measures a total energy of 0.52 J over a period of 32 s. How many photons per second are being emitted by the laser?

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Textbook Question

A stellar object is emitting radiation at 3.55 mm. a. What type of electromagnetic spectrum is this radiation? b. If a detector is capturing 3.2×108 photons per second at this wavelength, what is the total energy of the photons detected in 1.0 hour?

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Textbook Question

Molybdenum metal must absorb radiation with a minimum frequency of 1.09 * 1015 s - 1 before it can eject an electron from its surface via the photoelectric effect. (a) What is the minimum energy needed to eject an electron?

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