In the industrial production of H2 from water gas the CO2 produced along with the H2 is removed by

Analysis of the Question

The question asks for the industrial method used to remove carbon(IV) oxide ($CO_2$) from a mixture of hydrogen ($H_2$) and $CO_2$ (often called "water gas shift" products).

Concept Explanation

In the industrial production of hydrogen (the Bosch process), water gas ($CO + H_2$) is reacted with steam to produce more hydrogen and carbon(IV) oxide:

To obtain pure hydrogen, the $CO_2$ must be separated from the mixture. Industrially, this is achieved by taking advantage of the solubility of $CO_2$ in water. When the gas mixture is subjected to high pressure, $CO_2$ dissolves readily in water, while hydrogen remains as a gas.

Step-by-Step Solution

1. Analyze the options: • Option B: Phosphorus(V) oxide is a drying agent used to remove water vapor, not $CO_2$. • Option C: Limewater ($Ca(OH)_2$) reacts with $CO_2$ to form a precipitate, but this is a laboratory test for $CO_2$, not an efficient industrial-scale removal method for large volumes of gas. • Option D: Ammoniacal copper(I) chloride is used specifically to remove carbon(II) oxide ($CO$), not $CO_2$. • Option A: Washing under pressure is the standard industrial technique. By scrubbing the gas mixture with water under high pressure, $CO_2$ is dissolved and washed away, leaving the hydrogen gas behind.

2. Conclusion: The industrial process relies on the physical solubility of $CO_2$ in water, which is significantly enhanced under high pressure.

Final Answer

The correct option is A.

Exam Tip

When dealing with industrial gas purification questions:

• $CO_2$ removal: Think of "washing under pressure" or using alkaline solutions like potassium hydroxide ($KOH$).
• $CO$ removal: Think of "ammoniacal copper(I) chloride."
• Drying: Think of "concentrated $H_2SO_4$" or "phosphorus(V) oxide."