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CH1012
CARBONIC ACID
Carbon dioxide is present as a minor gas
in the atmosphere (0.038%). The reaction
of carbon dioxide with water forms
carbonic acid.  CO2(aq) + H2O(aq) ® H2CO3(aq)
• Carbonic acid H2CO3 is the most important naturally occurring acid.  (this hydroxide is a weak acid)     H2CO3(aq) D HCO3-(aq) + H+(aq)
• The exogenic cycle treats the crust of the Earth as a large acid-base titration system.
Carbonic acid in rain water dissolves the basic rocks which are carried away to oceans. The components form sediments which are then compressed back into rocks.