During photosynthesis `H_2O` is __________.

Answer

**Step-by-Step Solution:**

1. **Understanding Photosynthesis**: Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy, using carbon dioxide (CO2) and water (H2O) as raw materials.

2. **Role of Water (H2O)**: During photosynthesis, plants absorb water from the soil. This water is crucial for the process as it provides the necessary hydrogen atoms.

3. **Oxidation of Water**: In the process of photosynthesis, water (H2O) is oxidized. Oxidation refers to the loss of electrons. In this case, the water molecules lose electrons and are split into oxygen (O2) and hydrogen ions (H+).

4. **Reduction of Carbon Dioxide**: While water is oxidized, carbon dioxide (CO2) is reduced. Reduction refers to the gain of electrons. The hydrogen from the oxidized water combines with carbon dioxide to form glucose (C6H12O6).

5. **Products of Photosynthesis**: The overall reaction of photosynthesis can be summarized as:
- 6CO2 + 6H2O + light energy → C6H12O6 + 6O2
This means that six molecules of carbon dioxide and six molecules of water, in the presence of light energy, produce one molecule of glucose and six molecules of oxygen.

6. **Conclusion**: Therefore, during photosynthesis, water (H2O) is oxidized.

**Final Answer**: During photosynthesis, H2O is oxidized.

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