Photosynthesis
The overall reaction by which plants use light energy to convert carbon dioxide and water into glucose and oxygen.
Formula
Variables
Example
6 molecules of CO₂ + 6 of water yield 1 glucose + 6 O₂
How it works
Photosynthesis is the chemical process that stores light energy in the bonds of glucose. In chloroplasts, chlorophyll absorbs light and uses that energy to split water, release oxygen, and drive reactions that combine carbon dioxide into carbohydrate. The balanced equation matters because it shows the atoms are conserved: six carbons, twelve hydrogens, and eighteen oxygens appear on both sides once the products are counted.
When to use it
Use this equation when studying plant metabolism, energy transfer, or biomass production in biology and chemistry. It is also useful for stoichiometry problems involving how much glucose or oxygen can be produced from given amounts of carbon dioxide and water.
Worked example, step by step
Suppose a plant has 18 moles of CO2 and 18 moles of H2O available. Step 1: Use the balanced equation: 6 CO2 + 6 H2O -> 1 C6H12O6 + 6 O2 Step 2: Find the limiting reactant. The ratio CO2:H2O is 1:1, and the available amounts are equal, so neither is in excess. Step 3: Scale the reaction by 3, because 18 ÷ 6 = 3. Step 4: Glucose produced = 1 × 3 = 3 moles of C6H12O6 Step 5: Oxygen produced = 6 × 3 = 18 moles of O2 Final answer: 18 moles of CO2 and 18 moles of H2O produce 3 moles of glucose and 18 moles of oxygen.
Common mistakes to avoid
- Forgetting that light is the energy input, not a reactant that gets used up
- Using the equation as if it happens in one step without chlorophyll and chloroplasts
- Miscalculating mole ratios by not matching the coefficients in the balanced equation
Did You Know?
Photosynthesis produces virtually all the oxygen in our atmosphere and sits at the base of nearly every food chain.
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