Unit 2 Green chemistry Flashcards
What is green chemistry?
The design of chemical process and products that reduce and eliminate the production and use of hazardous chemicals.
What is thermal decomposition?
When something breakers up because of heat. It occurs to hydrates and carbonates.
What are the basics of green chemistry?
Changing to renewable resources.
Finding alternatives to hazardous chemicals.
Developing new catalysts.
Being more energy efficient and using renewable energy.
Reducing waste and pollution.
What are the two main approaches for using renewable resources?
Extracting useful chemicals directly from plants.
Break down plant material into simple chemicals for further use, like fermenting ethanol.
How is ozone created?
Sun light causes O₂ molecules to split into O• free radicals. These then react to O₂ to give O₃.
How does the ozone help us?
When is absorbs UV light it splits into a free radical and O₂ again protecting us from skin cancer and really bad sunburn.The ozone is created as fast as it is destroyed by the UV light.
How do CFCs damage the ozone?
They go into the stratosphere where the UV light causes them to split up CCl₃F→ CCl₂F• + Cl•
The free radicals are catalysts that react with ozone to form an intermediate.
Cl• + O₃ → O₂ + ClO•
ClO• + O₃→ 2O₂ + Cl• The chlorine acts as a catalyst and the overall reaction is 2O₃ → 3O₂.
Where is the ozone layer?
The stratosphere.
How is the ozone destroyed with out CFCs?
The uv radiation can cause O₃ to form O• and O₂ again. If there is no artificial interference then it is created as quickly as it is being destroyed.
How are CFCs made?
By replacing all the hydrogens in an alkane with chlorine and fluorine.
Other than CFCs, what can damage the ozone?
NO• free radicals.
They come from nitrogen oxides and also act as catalysts.
NO•+ O₃ → O₂ + NO₂•
NO₂ + O₃ → 2O₂ + NO•
Why is a high atom economy wanted?
It reduced waste and makes the best use of resources.
What are the main green house gases?
Water vapour, CO₂, methane, NO₂, ozone
What radiation causes the green house effect?
Infrared
What is the disadvantage of using alkanes to replace CFCs ?
They act as green house gas.
