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CH3041
PHOTOSYNTHESIS
• Energy for most
of the redox chemistry at the Earths
surface comes originally from photosynthesis: hn DG
+478 kJ / mol
CO2(g) + H2O ® {CH2O} + O2(g)
Solar
energy (lots of) is required to drive this thermodynamically unfavoured rxn.
• Organic
matter {CH2O} is the reductant
(it is oxidised back to CO2) which fuels subsequent redox rxns releasing stored
bond energy.
(it is oxidised back to CO2) which fuels subsequent redox rxns releasing stored
bond energy.
• Oxygen is the normal oxidant (e- sink).
• The carbon
cycle supplies electrons to many other elemental cycles. (0)
® (IV) + 4e-
