The gas that ammoniacal solution of CuCl$_2$ is used to absorb from producer or water gas is

Analysis of the Question

The question asks for the specific gas component in producer gas or water gas that is selectively absorbed by an ammoniacal solution of copper(I) chloride ($CuCl_2$ or more accurately $CuCl$).

Concept Explanation

Producer gas and water gas are both mixtures of gases used primarily as industrial fuels.

• Producer gas: A mixture of Carbon(II) oxide ($CO$) and Nitrogen ($N_2$).
• Water gas: A mixture of Carbon(II) oxide ($CO$) and Hydrogen ($H_2$).

In industrial chemistry, it is often necessary to purify these gases. Ammoniacal copper(I) chloride is a specific chemical reagent used in gas analysis and purification. It reacts with Carbon(II) oxide ($CO$) to form a coordination complex, effectively removing it from the gas mixture. The reaction is:

Step-by-Step Solution

1. Identify the components: We know producer gas contains $CO$ and $N_2$, while water gas contains $CO$ and $H_2$.
2. Evaluate the reagent: Ammoniacal copper(I) chloride is a well-known absorbent for Carbon(II) oxide ($CO$).
3. Eliminate other options: • $H_2$ and $N_2$ do not react with ammoniacal copper(I) chloride. • $CO_2$ is typically absorbed by alkaline solutions like Potassium Hydroxide ($KOH$), not copper(I) chloride.
4. Conclusion: Since $CO$ is the common component in both gases that reacts with this specific reagent, it is the gas being absorbed.

Identification of the Answer

The correct option is B.

Exam Tip

Remember the "Absorbent Rule" for gas analysis:

• $CO_2$ is absorbed by $KOH$ (Potassium hydroxide).
• $O_2$ is absorbed by Alkaline pyrogallol.
• $CO$ is absorbed by Ammoniacal copper(I) chloride.
• $H_2$ is often removed by passing the gas over heated copper(II) oxide ($CuO$).