Photosynthesis is the process by which CO₂ is converted to an organic compound. The complete reaction is as follows; 6CO₂ + 6H₂O --> C₆H₁₂O₆ + 6O₂ stoichiometry of CO₂ to C₆H₁₂O₆ is 6:1 For 1 mol of C₆H₁₂O₆ to be formed - 6 mol of CO₂ is required Therefore for 3.21 mol of C₆H₁₂O₆ to be formed - 6 x 3.21 mol of CO₂ required Number of moles required are - 19.26 mol of CO₂