To determine which equation best represents the conservation of matter, we must ensure that the number of atoms of each element on the reactants side matches the number on the products side.
1. **3H2O + 3CO2 → C6H12O6 + 6O2**
- Reactants: 3 H2O (6 H, 3 O) + 3 CO2 (0 C, 6 O) = 6 H, 3 C, 9 O
- Products: C6H12O6 (6 C, 12 H, 6 O) + 6 O2 (0 C, 12 O) = 6 C, 12 H, 6 O
- **Not balanced.**
2. **6H2O + 6CO2 → C6H12O6 + 6O2**
- Reactants: 6 H2O (12 H, 6 O) + 6 CO2 (6 C, 12 O) = 6 C, 12 H, 18 O
- Products: C6H12O6 (6 C, 12 H, 6 O) + 6 O2 (0 C, 12 O) = 6 C, 12 H, 18 O
- **Balanced.**
3. **6H2O + 6CO2 → C3H6O3 + 3O2**
- Reactants: 6 H2O (12 H, 6 O) + 6 CO2 (6 C, 12 O) = 6 C, 12 H, 18 O
- Products: C3H6O3 (3 C, 6 H, 3 O) + 3 O2 (0 C, 6 O) = 3 C, 6 H, 9 O
- **Not balanced.**
4. **6H2O + 10CO2 → C6H12O6 + 4O2**
- Reactants: 6 H2O (12 H, 6 O) + 10 CO2 (10 C, 20 O) = 10 C, 12 H, 26 O
- Products: C6H12O6 (6 C, 12 H, 6 O) + 4 O2 (0 C, 8 O) = 6 C, 12 H, 14 O
- **Not balanced.**
The equation **6H2O + 6CO2 → C6H12O6 + 6O2** is the only one that accurately represents the conservation of matter, as it balances both reactants and products.