Unit 8 - Carbon
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Can you draw graphite
Yes? Good
Why can graphite be used as a lubricant
The layers of graphite can slide over each other.
Why is diamond used for cutting tools
It’s giant lattice structure and lack of free electrons means that it is very strong
Why is carbon monoxide poisonous
It replaces the oxygen in the haemoglobin in your red blood cells, reducing the capacity of your blood to carry oxygen
Why does the incomplete combustion of fuels produce carbon monoxide
Because it doesn’t finish reacting with the oxygen in the air to form CO2 instead of CO
Describe the laboratory preparation of CO2 (metal carbonate)
Heat a metal carbonate. If a metal carbonate is heated it decomposes (not burn) evolving CO2 gas and leaving the metal oxide
Thermal decomposition of a metal carbonate
Metal carbonate -heat-> metal oxide + carbon dioxide
Describe the laboratory preparation of CO2 (acid + carbonate)
If a dilute acid is added to a metal carbonate in the cold, CO2 is produced Eg CaCO3 + 2HCl –> CaCl2 + H2O + CO2
What’s the purpose of concentrated sulphuric acid in the production of CO2 (acid + carbonate)
It is a drying agent (absorbs water)
How can CO2 be collected
Downward delivery (it’s denser than air) Using a gas syringe Over hot water
Is CO2 soluble in water
It’s fairly soluble in cold water, not very soluble in hot water
CO2 + water
CO2 (g) + H2O (l) –> H2CO3 (aq) Carbonic acid is fairly weak (pH5)
Define an acid
An acid is a source of H+ ions
Uses of CO2
In fizzy drinks In fire extinguishers
Why can CO2 be used in fizzy drinks
Because it is soluble in cold water so will stay dissolved in the drink until it reaches your warm mouth where it will fizz because CO2 is less soluble in warm water
Why is CO2 used in fire extinguishers
Not flammable (only magnesium burns it it) Denser than air, it forms a layer over the fire so O2 can’t reach it Doesn’t conduct electricity
Can you draw diagrams of diamond
Yes? Good.