To determine the missing coefficient for water in the equation for cellular respiration, we can use the law of conservation of matter, which states that matter cannot be created or destroyed in a chemical reaction. This means that the number of each type of atom on the reactant side must equal the number of each type of atom on the product side.
The balanced equation for cellular respiration is:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + ?H₂O + Energy
Now, let's break this down:
-
Glucose (C₆H₁₂O₆):
- Carbon (C): 6
- Hydrogen (H): 12
- Oxygen (O): 6
-
Oxygen (6O₂):
- This contributes 12 Oxygen atoms (6 O₂ = 12 O).
Total on the Reactant Side:
- Carbon: 6
- Hydrogen: 12
- Oxygen: 6 (from glucose) + 12 (from oxygen) = 18
On the Product Side:
- Carbon (from 6CO₂): 6 (6 CO₂ contributes 6 Carbons)
- Oxygen (from 6CO₂): 12 (6 CO₂ contributes 12 Oxygens)
Now we need to balance the hydrogen and find the amount of water.
Oxygen balance: There are 12 Oxygens from 6 CO₂. The total number of Oxygens needed on the product side is 18 (from above). Since we already have 12 Oxygens from the CO₂, the remaining Oxygens must come from the water (H₂O):
Total Oxygens from H₂O = 18 (needed) - 12 (from CO₂) = 6 Oxygens
Since each water molecule (H₂O) contains 1 Oxygen, it means we need 6 H₂O molecules.
Thus, the missing coefficient for water is 6.
Final balanced equation:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
So, the answer is 6.