Question

Which gas was absent in Miller experiment?

• A. \(O_2\)
• B. \(H_2\)
• C. \(NH_3\)
• D. \(CH_4\)

Hint:

Remember the gas combination used in the Miller-Urey experiment as CHNH: Methane (\(CH_4\)), Ammonia (\(NH_3\)), Hydrogen (\(H_2\)), and Water Vapour (\(H_2O\)). Free oxygen was absent.

Answer 1

The Correct Option is A

Concept: The Miller-Urey experiment, conducted in 1953 by Stanley Miller and Harold Urey, was designed to test the hypothesis proposed by Oparin and Haldane regarding the origin of life on Earth. According to this hypothesis, the primitive atmosphere of Earth was reducing in nature and contained simple inorganic gases. When these gases were subjected to energy sources such as lightning, they could form complex organic molecules that are essential for life. The experiment successfully demonstrated the abiotic synthesis of amino acids from simple gases under simulated primitive Earth conditions.

Step 1: Identify the gases used in the experiment. The apparatus contained a mixture of gases believed to represent the primitive atmosphere. These gases were: \[ CH_4,\quad NH_3,\quad H_2,\quad H_2O \] where:
• \(CH_4\) = Methane
• \(NH_3\) = Ammonia
• \(H_2\) = Hydrogen
• \(H_2O\) = Water vapour

Step 2: Understand the nature of primitive atmosphere. The primitive atmosphere was considered reducing in nature. Free molecular oxygen was absent because oxygen is highly reactive and would have oxidized newly formed organic compounds. Therefore, oxygen was deliberately excluded from the experimental setup.

Step 3: Draw the conclusion. Among the given options, oxygen was not present in the Miller-Urey experiment. \[ \boxed{O_2} \] Hence, the correct answer is \[ \boxed{(A)\ O_2} \]