Which equation correctly represents the balanced photosynthesis reaction?

• A. CO2 + H2O → C6H12O6 + O2
• B. 2CO2 + 2H2O → C6H12O6 + 2O2
• C. 6CO2 + 6H2O → C6H12O6 + 6O2
• D. CO2 + H2O → C6H12O6 + O2

Answer: (C)

Balancing atoms is the key idea. In photosynthesis, one glucose molecule needs six carbon atoms, twelve hydrogens, and six oxygens from the reactants. Using six carbon dioxide and six water molecules provides exactly that: six carbons from CO2, twelve hydrogens from H2O, and a total of eighteen oxygens (six in glucose and twelve released as O2).

Check the counts: carbons — 6 on both sides; hydrogens — 12 on both sides; oxygens — 18 on both sides. This makes the equation consistent and represents the process correctly: six CO2 plus six H2O yields C6H12O6 plus six O2.

Other common forms omit the proper coefficients and thus don’t conserve atoms, leading to imbalanced equations.