air, water, sulfur Flashcards
What are the two tests for the presence of water
It turns anhydrous copper sulfate from white to blue.
It turns anhydrous cobalt chloride from blue to pink.
We normally use cobalt chloride paper which is absorbent paper soaked in cobalt chloride solution
and kept dry in a desiccator.
Where is water stored
Water is stored in dams and reservoirs
how is water treated
Water treatment essentially involves the stages, filtration, sedimentation, (ozone treatment) and
chlorination
Average percent composition of air
nitrogen (N2) 79 oxygen (O2) 20 argon (Ar) 0.9 carbon dioxide (CO2) 0.03 others 0.07
what is sulfur dioxide
Sulfur dioxide formed by the combustion of sulfur that can be found in many of our fossil fuels (e.g.
coal). The sulfur dioxide reacts with water in the clouds and when it rains it forms sulfurous acid
(acid rain).
What is nitrogen oxide
Nitrogen oxides (NOx gases) form from the reaction between nitrogen and oxygen at high
temperature and pressure in the engines of motor vehicles. These also contribute to acid rain, and
are a major component of photochemical smog, especially in places like Los Angeles.
what is carbon monoxide
Carbon monoxide from incomplete combustion in motor vehicle engines. Carbon monoxide has a
greater affinity (bonds more strongly and permanently) with haemoglobin, decreasing the amount of
oxygen distributed around the body, causing drowsiness, black-outs and possible death by
asphyxiation.
What is lead
Lead containing compounds from the combustion of petrol containing lead. Lead and other heavy
metals, like mercury, cause brain damage and nervous system problems known as heavy metal
poisoning. Many countries now use unleaded fuel by putting in additives to the fuel to replace the
lead
what is corrosion
Most metals will react with water and oxygen. The metal atoms lose electrons to form ions. When this
oxidation occurs in nature - in seawater or moist air - the process is known as corrosion. Most common
metals corrode - except silver and gold - and this presents problems.
What is rusting
Rusting is the corrosion of iron metal to form a red-brown compound - hydrated iron(III) oxide,
Fe2O3.xH2O. Both oxygen and water must be present for rusting to occur.
how to prevent rust
There are two main ways in which rusting can be reduced.
• covering with a protective coat.
• preventing oxidation of the metal.
Methods of covering metal
- Painting of cars etc.
- Greasing of metal parts
- Oiling of woks and other cooking utensils
- Plastic covering on electric wires
- Galvanising - zinc coat for galvanised steel
- Tin plating - in cans
- Chromium plating of car parts
Properties of sulfur
Brittle yellow solid.
Melting Point (m.p.) of 119 °C and a Boiling Point (b.p.) of 445 °C.
Non-conductor of heat and electricity.
Insoluble in water but it will dissolve in some organic solvents e.g. CS2 (carbon disulfide) as it is also
non-polar.
Burns with a blue flame when lit.
