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Chapter 18: Problem 25

(a) What is the difference between chlorofluorocarbons and hydrofluorocarbons? (b) Why are hydrofluorocarbons potentially less harmful to the ozone layer than CFCs?

Short Answer

Expert verified
(a) The difference between chlorofluorocarbons (CFCs) and hydrofluorocarbons (HFCs) is that CFCs contain chlorine, fluorine, and carbon, while HFCs contain hydrogen, fluorine, and carbon. CFCs have the formula C_xCl_yF_z, and HFCs have the formula C_xH_yF_z. (b) Hydrofluorocarbons are potentially less harmful to the ozone layer than CFCs because they do not contain chlorine atoms, which are responsible for ozone depletion. CFCs release chlorine molecules into the atmosphere that react with ozone and break it down, while HFCs do not participate in this ozone-destruction cycle.

Step by step solution

01

(1. Understand Chlorofluorocarbons (CFCs))

CFCs are a family of synthetic compounds containing chlorine, fluorine, and carbon. They have been widely used as propellants, refrigerants, and solvents. Their formula is generally written as C_xCl_yF_z. Some common examples include CFC-12 (CF2Cl2) and CFC-11 (CFCl3).
02

(2. Understand Hydrofluorocarbons (HFCs))

HFCs are a group of synthetic compounds containing hydrogen, fluorine, and carbon. They were introduced as alternatives to CFCs, in response to concerns about ozone depletion. Their formula is typically written as C_xH_yF_z. Some examples of HFCs include HFC-134a (CH2FCF3) and HFC-152a (CH3CHF2).
03

(3. Identify the Difference between CFCs and HFCs)

The notable difference between CFCs and HFCs is the presence (or absence) of chlorine. CFCs contain chlorine, fluorine, and carbon, whereas HFCs contain hydrogen, fluorine, and carbon. To answer part (a) of the exercise, the difference between chlorofluorocarbons and hydrofluorocarbons is that CFCs contain chlorine in their composition, while HFCs do not.
04

(4. Discuss the Harmful Effects of CFCs on the Ozone Layer)

CFCs are known to contribute to the depletion of the ozone layer by releasing chlorine molecules through a series of photodissociation reactions. When the released chlorine reacts with ozone (O3) molecules in the stratosphere, it breaks them down into oxygen (O2) molecules and a chlorine-monoxide (ClO) molecule. This process reduces the overall concentration of ozone in the stratosphere, leading to the depletion of the ozone layer.
05

(5. Explain Why HFCs are Potentially Less Harmful to the Ozone Layer than CFCs)

Since HFCs do not contain chlorine in their composition, their potential for depleting the ozone layer is significantly reduced. Unlike CFCs, HFCs do not release chlorine molecules into the atmosphere, so they do not participate in the ozone-destruction cycle. Therefore, HFCs are regarded as more environmentally friendly alternatives to CFCs. To answer part (b) of the exercise, hydrofluorocarbons are potentially less harmful to the ozone layer than CFCs because they do not contain chlorine atoms, which are responsible for ozone depletion.

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