Properties of Carbon Dioxide
Comment on the following properties of CO2 and discuss a use of CO2 that
relies on that property.
Solubility_
Quite soluble in water. Solubility decreases as temperature rises.
Use
Gives you the bubbles in fizzy drinks. The fizz in Beer and champagne is
from carbon dioxide produced by yeast during fermentation.
Density
More dense than air – will sink to the ground
Use
Fire extinguishers. The dense carbon dioxide sits on top of the fire
preventing oxygen reaching the flames and thus extinguishing them.
Acidity
Carbon dioxide forms a weak acid when dissolved in water (non metal
oxides are acidic) pH about 3-4
Equation which shows CO2 behaving as an acid:
CO2 + H2O → H2CO3 → H+(aq) + HCO3-(aq) (these reactions are all reversible)
Significance in Limestone Geology?
Carbonic acid, H2CO3, dissolves limestone forming caves.
Equations?
H2CO3(aq) + CaCO3(s) → Ca(HCO3)2(aq) (limestone dissolves)
Ca(HCO3)2(aq) → H2CO3(aq) + CaCO3(s) (limestone reforms – tufa, stalagmites and
stalactites form)
Ca(HCO3)2 (aq) is what makes tap water “hard” in some parts of the
country.