Which term refers to nitrogen present as organic molecules dissolved in water?

• A. Dissolved Organic Carbon
• B. Endothermic
• C. Dissolved Organic Nitrogen
• D. Entropy

Answer: (C)

Nitrogen in water can be inorganic (like nitrate or ammonium) or organic. When nitrogen is part of organic molecules that are dissolved in the water, we call it dissolved organic nitrogen. This includes compounds such as amino acids and urea that are present dissolved rather than attached to particles. The other options don’t fit: dissolved organic carbon refers to carbon-containing compounds, not nitrogen; endothermic describes heat absorption in a reaction; entropy is a measure of disorder. So the term that specifically names nitrogen in dissolved organic form is dissolved organic nitrogen.