Chemical equations you may need to know

Complete combustion:
any fuel + O2 --> CO2 + H2O
Balance the C, then H then Os.

Incomplete combustion
any fuel + O2 --> CO + H2O

Reaction of CO2 with limewater:
Ca(OH)2 + CO2 --> CaCO3 + H2O
-------> in excess CO2 if you keep bubbling CO2 through: CaCO3 + CO2 + H2O --> Ca(HCO3)2

Fermentation:
C6H12O6 --> C2H5OH + CO2

Production of CO2 in lab:
CaCO3 + HCl --> CaCl2 + CO2 + H2O