Which of the following reactions is an endergonic reaction?

• A. Respiration
• B. Photosynthesis
• C. Rusting of iron
• D. Combustion of glucose

Answer: (B)

Verified step by step guidance

1. Understand the concept of endergonic reactions: Endergonic reactions are chemical reactions that require an input of energy to proceed. They are characterized by a positive change in Gibbs free energy (ΔG > 0).
2. Identify the nature of each reaction: Analyze each given reaction to determine whether it absorbs or releases energy.
3. Photosynthesis: This process involves the conversion of carbon dioxide and water into glucose and oxygen using sunlight energy. It is an endergonic reaction because it requires energy input from sunlight.
4. Respiration: This is the process of breaking down glucose into carbon dioxide and water, releasing energy. It is an exergonic reaction (ΔG < 0).
5. Rusting of iron and combustion of glucose: Both are exergonic reactions as they release energy. Rusting involves the oxidation of iron, and combustion involves the oxidation of glucose, both releasing energy.