Unit 14 Flashcards
What gases are in the air
Nitrogen 78%
Oxygen 21%
How can nitrogen and oxygen be separated?
Can be separated by fractional distillation. This works because the gases in air have different boiling points
Uses for oxygen
- In hospitals
People with breathing problems are given oxygen through oxygen tanks covering the nose and mouth, they also use oxygen tents - Welding metals
A mixture of oxygen and ethanol is used in oxy-acetylenes torches that are used in welding metals
The main air pollutants
Carbon monoxide
Sulphur dioxide
Nitrogen oxides
Lead compounds
How is Carbon monoxide formed?
Forms when the carbon compounds in fossil fuels burn in too little air.
E.g inside car engines and furnaces
What harm does carbon monoxide do
Poisonous even in low concentrations. It reacts with the haemoglobin in blood, and prevents it from carrying oxygen around the body- so you die from oxygen starvation
How is sulphur dioxide formed
Sulphur occurs naturally in the fossil fuels (mainly in coal and oil) and forms sulphur dioxide when it burns
What harm does sulphur dioxide
Irritates the eyes and throat, and cause respiratory (breathing) problems
Dissolves in rain to form acid rain, which damages buildings, trees and plants and kills fish and other river life
How are nitrogen oxides formed
Form when the nitrogen and oxygen in air react together inside hot car engines, and in hot furnaces
What harm does nitrogen oxides do
Cause respiratory problems
Dissolves in rain to form acid rain
How lead compounds are formed
A compound called tetra-ethyl lead was added to petrol to help it burn smoothly in engines. On burning, it produced particles of other lead compounds, mainly lead halides such as PbBrCl
What harm does lead compounds do
Lead damages children’s brains. It damages the kidneys and nervous systems in adults
Ways to reduce pollution
Use less fossil fuels
Switch to clean sources of power
Try to find ways to store CO2 and not let it escape to the atmosphere
Waste gases that are disposed of through exhaust pipes
Oxides of nitrogen, which form when nitrogen and oxygen from the air react in the hot engines. This causes acid rain.
Carbon monoxide, CO, which forms when carbon compounds burn in insufficient oxygen. It is poisonous.
Unburnt hydrocarbons from the petrol. These can cause cancer.
What is a catalytic converter
To tackle the problem of harmful gases being released into the atmosphere, modern car exhausts contain a catalytic converter. In this, the harmful gases. The are absorbed onto catalysts, and react to produce harmless gases. The converter usually has two catalyst compartments.
The usual catalysts are the transitions metals platinum, palladium, and rhodium. They are coated onto ceramic support. This is in the form of beads, of a honeycomb , to give a large surface area for absorbing gases. The harmless products flow out the exhaust pipe.
