Ultraviolet radiation and radiation of shorter wavelengths...

Name: Problem 73, Chapter 2: Chemistry: Structure and Properties
Uploaded: 2021-08-26T01:19:49-08:00
Duration: 3 min 41 s
Channel: Tracy Tourville
Description: Ultraviolet radiation and radiation of shorter wavelengths can damage biological molecules because they carry enough energy to break bonds within the molecules. A typical carbon carbon bond requires 348 kj/mol to break. What is the longest wavelength of radiation with enough energy to break carbon carbon bonds?

Ultraviolet radiation and radiation of shorter wavelengths can damage biological molecules because they carry enough energy to break bonds within the molecules. A typical carbon carbon bond requires 348 kj/mol to break. What is the longest wavelength of radiation with enough energy to break carbon carbon bonds?

Ultraviolet radiation and radiation of shorter wavelengths can damage biological molecules because they carry enough energy to break bonds within the molecules. A typical carbon carbon bond requires
348 kj/mol to break. What is the longest wavelength of radiation with enough energy to break carbon carbon bonds?

Key Concepts

Planck's Equation

Planck's equation, expressed as E = hc/?, defines the relationship between the energy (E) of a photon and its wavelength (?), with h representing Planck's constant and c the speed of light. This formula is fundamental to understanding how different wavelengths of electromagnetic radiation correspond to specific energy levels, which is critical in determining whether a photon has enough energy to initiate chemical reactions or break molecular bonds.

Bond Dissociation Energy

Bond dissociation energy is the amount of energy required to break a specific chemical bond in a molecule. It is typically expressed in energy per mole, establishing a threshold that light or other energy sources must meet or exceed to break the bond. This concept is key in fields like photochemistry and molecular physics, where assessing the energy from electromagnetic radiation against molecular bond strengths helps predict chemical behavior.

Unit Conversion from Mole to Photon Energy

In order to apply the energy-wavelength relationship to individual photons, it is necessary to convert the bond dissociation energy given per mole into the energy per single molecule. This is achieved by using Avogadro's number, which links the macroscopic energy units (kJ/mol) to microscopic energy scales appropriate for single photons, enabling careful comparison with the photon energy derived from Planck's equation.

Electromagnetic Radiation Spectrum

The electromagnetic radiation spectrum encompasses various types of radiation, from radio waves to gamma rays, each characterized by different wavelengths and energies. Understanding which segment of the spectrum, such as ultraviolet light, contains photons with sufficient energy to initiate processes like chemical bond breaking, is essential in applications spanning from material science to biological damage assessment.

Transcript

00:01 So this question deals with wavelength and frequency and the relationship to energy.

00:07 So over here in this box, we have a couple of equations we're going to need to use.

00:12 Energy is related to frequency times planks constant.

00:18 So supplied planks constant here as the 6 .63 times 10 in the negative 4, 34 joules seconds.

00:27 And wavelength and frequency are related by the.

00:30 Speed of light.

00:31 I've supplied that number here.

00:34 Now this is the information that we were supplied with that for a mole of carbon -carbon bonds, 348 kilojoules of energy is required to break the bonds, for every mole of carbon -carbon bonds we have.

00:48 Well, the units that we're going to be utilizing in ultimately determining the frequency and wavelength associated with that energy is joules.

00:59 So i've just rewritten that 4348 kilojoules as 348 ,000 joules per mole.

01:06 Well, here's what we know.

01:07 That gives us the energy associated with the mole of carbon carbon bonds, but we want to look at an individual carbon carbon bond.

01:16 And so what's in a mole? avogadro's number.

01:19 So every mole of carbon carbon bonds contains this many 6 times 0, 2 times 10 to 23rd carbon bonds.

01:27 So if we rewrite that for an individual bond, we get this much energy associated with an individual bond.

01:36 That's the energy, nor this down here...

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