What is the photosynthesis reaction?

Answer 1

Carbon Dioxide + Water --> Glucose + Oxygen

CO2 + H2O --> C6H12O6 + O2

Balancing the equation, it becomes:

6CO2 + 6H2O --> C6H12O6 + 6O2

Note that the reactions also require light and energy (usually written in smaller letters above or below the arrow signs).

The balanced equation is the one you should write during exams, unless they ask you otherwise (which would be very odd).

Answer 2

The general equation for photosynthesis is:
2n CO2 + 2n DH2 + photons ? 2(CH2O)n + 2n DO or
Carbon dioxide + electron donor + light energy ? carbohydrate + oxidized electron donorIn oxygenic photosynthesis water is the electron donor and, since its hydrolysis releases oxygen, the equation for this process is:
2n CO2 + 4n H2O + photons ? 2(CH2O)n + 2n O2 + 2n H2O or
carbon dioxide + water + light energy ? carbohydrate + oxygen + water