1. Arrange the following compounds in a series from most reduced to most oxidized

• CO₂
• CH₄
• H₃COOH
• H₂C=O
• CH₃CH₂OH

2. Which of the following compounds can serve as energy donors? Do such compounds need to highly reduced or highly oxidized?

• CO₂
• CH₄
• H₂O
• H₂
• H₂S
• O₂
• SO₄⁼
• NO₃^-
• NH₃
• NO₂^-

3. Which of the compounds in the list above can serve as electron acceptors? Do such compounds need to highly reduced or highly oxidized?