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The Ozone Layer

Contains O3

Removes dangerous UV radiation.

The ozone is being destroyed and replaced at an equilibrium.

CFC's destroy the ozone. - CFCs are broken down by UV radiation. Chlorine free radicals are then formed.

The free radicals act as a catalyst.

CFCs are unreactive, non-flammable and non-toxic.

Nitrogen oxide, NO, free radicals destroy the ozone too.

Produced by cars, aircrafts and thunderstoms.

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Green Chemistry

Green chemistry means doing thing sustainably, by not using up the earths resources. 

Uses of renewable resources like plastics made from plant products rather than oil fractions.

Energy efficiency is also improved too.

Useful if chemical reactions have a good atom economy, to reduce waste.

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Climate Change

The sun emits visible light, UV radiation and infrared radiation.

Most is absorbed by atmospheric gases and some is reflected back into space.

Main greenhouse gases are water vapour, carbon dioxide and methane. 

They absorb IR radiation to make the bonds vibrate more. - They are polar. 

The extra vibrational energy is passed on by collisions giving other molecules more energy therefore raising the temperature. 

Water vapour is the largest contributant to greenhouse gases, but it remains constant. 

Anthropogenic change is climate change due to humans. 

Carbon footprint is the amount of greenhouse gases something releases.

Carbon neutral is activities that have no overall carbon emisson.

Petrol is no carbon neutral

Bioethanl is carbon neutral

Hydrogen gas is pretty much carbon neutral.

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Increases the rate of reaction by providing an alternative route with a lower activation energy. 

Homogenous catalysts - is in the same state as the reactant. E.g. gas = gas. 

Speeds up reactions by forming one intermediate compound with the reactant. 

Enthalpy profile will have two humps. 

Monitoring reaction rate

Use a gas syringe

Measure then mass, mass decreases as a gas is evolved. 

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Iodine-Sodium Thiosulfate

A way of finding the concentration of an oxidising agent.


Add a certain amount of potassium iodate (V), the oxidising agent, to excess of potassium iodine solution.

The iodate ions oxidise the iodide ions to iodine.


Titrate it till the iodine colour fades to pale yellow.

Calculate the moles of iodine.


Calculate the concentration of the oxidising agent.

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Dissolve in water

Chlorine - colourless

Bromine - Yellow/Orange

Iodine - Brown

Dissolve in hexane

Chlorine - colourless

Bromine - Orange/Red

Iodine - Pink/Violet

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They are reducing agents, and they oxidise other substances. 

The get less reactive down the group, so they are worse reducing agents. - Less oxidising.

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