Exercise about determining energy of light that breaks bonds

In summary, the conversation is about determining which types of light contain enough energy to break chemical bonds in biological molecules. The formula for calculating the energy of a photon is given and three types of light (infrared, visible, and ultraviolet) are mentioned. The individual attempts to calculate the energy for ultraviolet light using the given formula, but they are unsure how to fit the result into the given range of 250-800 kJ/mol. The expert summarizer notes that the individual needs to use Avogadro's number to complete the calculation.
  • #1
ducmod
86
0

Homework Statement


Hello!
Here is the quote of the exercise:
Excessive exposure to sunlight increases the risk of
skin cancer because some of the photons have
enough energy to break chemical bonds in biological
molecules. These bonds require approximately
250–800 kJ / mol of energy to break. The energy of a
single photon is given by E = hc / lambda where E is the
energy of the photon in J, h is Planck’s constant 6.626 * 10^(-34) J s
and c is the speed of light 3 * 10^8 m/s
Determine which kinds of light
contain enough energy to break chemical bonds in
biological molecules by calculating the total energy
in 1 mol of photons for light of each wavelength.
(a) infrared light (1500 nm)
(b) visible light (500 nm)
(c) ultraviolet light (150 nm)

Of course, everyone knows that it's ultraviolet, but I can't come up with a correct math. Please, explain
my mistakes:
(6.626 * 10^(-34) J s * 3 * 10^8 m/s) / (150 * 10^(-9)) = 1.3252 * 10^(-17)
which I don't see how to fit in 250–800 kJ / mol of energy

Thank you!
 
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  • #2
ducmod said:
in 1 mol of photons
 
  • #3
Do you mean that 1.3252 * 10^(-17) is for one photon, and I have to multiply this number by avogadro number?
I didn't quite understand your remark.
 
  • #4
ducmod said:
Do you mean that 1.3252 * 10^(-17) is for one photon, and I have to multiply this number by avogadro number?

That's exactly what you are asked to calculate, aren't you?
 

1. What is the purpose of determining the energy of light that breaks bonds?

The purpose of determining the energy of light that breaks bonds is to understand the chemical reactions that occur when light is absorbed by molecules. This can help in fields such as photobiology, photochemistry, and materials science.

2. How is the energy of light that breaks bonds measured?

The energy of light that breaks bonds is typically measured using spectroscopy techniques. This involves shining a beam of light onto a sample and analyzing the light that is absorbed or emitted by the molecules.

3. Which types of bonds can be broken by light energy?

Light energy can break various types of bonds, including covalent bonds, ionic bonds, and hydrogen bonds. The energy required to break these bonds depends on the strength of the bond and the wavelength of the light.

4. How does the energy of light affect the breaking of bonds?

The energy of light directly affects the breaking of bonds. When a molecule absorbs a photon of light, it gains energy and the bonds holding the atoms together can become weaker or break completely. The amount of energy needed to break a bond depends on the bond strength and the wavelength of the light.

5. What factors can influence the energy of light that breaks bonds?

The energy of light that breaks bonds can be influenced by several factors, including the type of bond, the wavelength of the light, and the environment in which the reaction takes place. Other factors such as temperature, pressure, and the presence of catalysts can also affect the energy required to break bonds with light.

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