Q. What happened to $NH_{3}$ present in the primary atmosphere during its conversion to the secondary atmosphere?
A) It got oxidized to $H_{2}$ and water
B) It was absorbed by photoautotrophs
C) Most of it got oxidized to nitrogen oxides
D) It concentration was decreased due to $O_{2}$ formation
Explanation
Oxygen releasing photosynthesis organisms on the primitive earth similar to the existing blue-green algae (cyanobacteria). They used water to get hydrogen and released oxygen. Addition of oxygen to the atmosphere started oxidizing methane and ammonia, hence they began to disappear $CH_{4} + 2O_{2} \rightarrow CO_{2} + 2H_{2}O$ $4NH_{3} + 3O_{2} \rightarrow 2N_{2} + 6H_{2}O$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.