A diagram shows a series of reactions involving solids P and T, and gases Q and U, and solutions R and S. Identify the substances and write equations for the reactions.

Here's the solution to the questions based on the provided diagram:

a) Name:

• (i) Solid P: Manganese(IV) oxide ($\text{MnO}_2$)
• (ii) Gas Q: Chlorine ($\text{Cl}_2$)
• (iii) Solid T: Lead(II) chloride ($\text{PbCl}_2$)
• (iv) Solid U: Sulfur ($\text{S}$)

b) Write an ionic equation for the formation of the reddish-brown liquid R.
The reddish-brown liquid R is formed from the reaction of chlorine gas (Q) with sodium iodide solution. Chlorine displaces iodide ions to form iodine.

$$\text{Cl}_2(g) + 2\text{I}^-(aq) \to 2\text{Cl}^-(aq) + \text{I}_2(aq)$$

c) Give a commercial application of solution S.
Solution S is formed from chlorine gas and cold dilute potassium hydroxide, containing potassium hypochlorite ($\text{KClO}$).

• Bleaching agent (e.g., in laundry) or disinfectant (e.g., in water treatment).

d) State and explain the observation made when a gas jar containing chlorine gas is inverted over a gas jar containing hydrogen sulphide gas.

• Observation: A white or yellowish solid is formed, and the yellow-green colour of chlorine gas disappears.
• Explanation: Chlorine gas ($\text{Cl}_2$) is a strong oxidizing agent that reacts with hydrogen sulfide gas ($\text{H}_2\text{S}$). Chlorine oxidizes hydrogen sulfide to solid sulfur ($\text{S}$), which appears as a white or yellowish solid, and is itself reduced to hydrogen chloride gas ($\text{HCl}$). $$\text{Cl}_2(g) + \text{H}_2\text{S}(g) \to \text{S}(s) + 2\text{HCl}(g)$$

4. Give a reason why chlorine is used in the manufacture of pesticides and germicides.
Chlorine is a strong oxidizing agent and is highly reactive. These properties allow it to be incorporated into organic compounds to synthesize various pesticides and germicides, or to act directly as a germicidal agent by disrupting microbial cell structures.