F322 Chemistry ( Module 4) OCR

Why is ozone essential to life on Earth?

Ozone absorbs UV radiation in the stratosphere - UV radiation damages genetic material causing skin cancer and killing simple organisms.

What catalyses the break down of O3 and give the equation?

CFCs and NOx from thunderstorms or aircrafts catalyse the breakdown of O3

R + O3 ---> RO + O2

RO + O ---> R + O2

R is CL . from a CFC or NO from a NOx

How are CO ,oxides of nitrogen and unburnt hydrocarbons formed and why are they problematic?

CL. is formed by photolysis of CFCs

NOx are produced by internal combustion engines e.g. aeroplanes.

CFCs break down the ozone, NOx react with ozone at a low level and creates photochemical smog. This causes respiratory ailments such as asthma

How does a catalytic converter decrease CO and NO emissions from internal combustion engines?

The hot exhaust gases pass over the catalytic surface and the harmful gases are converted into less harmful products, which are then released into the atmosphere.The CO and NO gas molecules diffuse over the catalytic surface of the metal. Some of the molecules are held on to the metal surface by adsorption.

Temporary bonds are fomed between the catalytic surface and the gas molecules.

These bonds hold the gas molecules in the correct postion on the metal surface where they react together.

After the reaction the CO2 and N2 products are desorbed from the surface and diffuse away from the catalytic surface

How do we monitor air pollution?

infra-red spectroscopy

Describe the 5 principles of chemical sustainability

Using industrial porcesses that reduce or eliminate hazardous chemicals and which involve the use of fewer chemicals

Designing processes with a high atom economy that minimise the production of waste materials

Using renewable resources such as plant-based substances

Seeking alternative energy sources such as solar energy, rather than consuming finite resources such as fossil fuels that will eventually be exhausted

Ensuring that any waste products produced are non-toxic and can be recycled or biodegraded by being broken down into harmless substances in the environment

What are the problems with chemical sustainability?

apparent benefits may be offset by unexpected and detrimental side-effects e.g. biodiesel uses grain crops and land needed for food, with poorer countries being worse affected.

What is being done to promote reduction of pollution levels?

International cooperation between developing countries and developed countries such as the Montreal Protocol and the Rio declaration on Environment and Development.