Describe the Kipp's apparatus method for the manufacture of H2S . Give a reaction to show H2S is a reducing agent. [4+1]

Manufacture of $\mathrm{H}{}_2\mathrm{S}$ by Kipp’s Apparatus

Kipp’s apparatus is a laboratory device used for the generation of gases like $\mathrm{H}{}_2\mathrm{S}$ on demand. It consists of three main parts:

1. Middle bulb: Contains the solid reactant.
2. Lower bulb: Contains the liquid reactant.
3. Delivery tube: Used to collect the gas.

Preparation of $\mathrm{H}{}_2\mathrm{S}$ using Kipp’s Apparatus

The apparatus is set up as follows:

• The middle bulb is filled with ferrous sulfide ($\mathrm{FeS}$).
• The lower bulb is filled with dilute hydrochloric acid ($\mathrm{HCl}$).

When the stopcock is opened, the acid drips onto $\mathrm{FeS}$ and the following reaction occurs:

$$\mathrm{FeS}+2\mathrm{HCl}\to \mathrm{FeCl}{}_2+\mathrm{H}{}_2\mathrm{S}\uparrow$$

The produced $\mathrm{H}{}_2\mathrm{S}$ gas is collected through the delivery tube. The advantage of this method is that the gas is generated only when needed, and the apparatus can be stopped by closing the stopcock.

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$\mathrm{H}{}_2\mathrm{S}$ as a Reducing Agent

$\mathrm{H}{}_2\mathrm{S}$ acts as a reducing agent because it can donate electrons (or hydrogen) to other substances, thereby reducing them while itself getting oxidized.

Example Reaction

When $\mathrm{H}{}_2\mathrm{S}$ reacts with sulfur dioxide ($\mathrm{SO}{}_2$), it reduces $\mathrm{SO}{}_2$ to sulfur ($\mathrm{S}$) and itself gets oxidized to sulfur ($\mathrm{S}$):

$$2\mathrm{H}{}_2\mathrm{S}+\mathrm{SO}{}_2\to 3\mathrm{S}+2\mathrm{H}{}_2\mathrm{O}$$

Here, $\mathrm{H}{}_2\mathrm{S}$ reduces $\mathrm{SO}{}_2$ to sulfur, demonstrating its reducing nature.