Demonstrate oxidizing and displacement properties of non-metallic compounds (oxygen, hydrogen, chlorine, hydrogen chloride, sulphur dioxide, nitrogen, ammonia and carbon dioxide)

An oxidizing agent is a substance that gains electrons during a chemical reaction. Non-metals tend to gain electrons because they are electronegative.

How Oxidizing Works

When a non-metal acts as an oxidizing agent, it accepts electrons from another substance and gets reduced:

$Cl_2 + 2e^- \rightarrow 2Cl^-$

$O_2 + 4e^- \rightarrow 2O^{2-}$

$N_2 + 6e^- \rightarrow 2N^{3-}$

Common Oxidizing Agents

Worked Example: Chlorine as Oxidizing Agent

When chlorine gas is bubbled through iron(II) chloride solution:

• Iron(II) ions lose electrons (are oxidized): $Fe^{2+} \rightarrow Fe^{3+} + e^-$
• Chlorine gains electrons (is reduced): $Cl_2 + 2e^- \rightarrow 2Cl^-$

Overall: $2Fe^{2+} + Cl_2 \rightarrow 2Fe^{3+} + 2Cl^-$

The pale green Fe²⁺ solution turns yellow/brown due to Fe³⁺ formation.

A more reactive non-metal can displace a less reactive non-metal from its compound. This is similar to metal displacement but involves non-metals.

Halogen Displacement Series

The reactivity order from strongest to weakest oxidizing agent:

Fluorine > Chlorine > Bromine > Iodine

A more reactive halogen will displace a less reactive one:

$2NaBr(aq) + Cl_2(g) \rightarrow 2NaCl(aq) + Br_2(l)$

$2KI(aq) + Cl_2(g) \rightarrow 2KCl(aq) + I_2(s)$

Practical Demonstration

When chlorine water is added to potassium iodide solution:

• The colourless solution turns brown due to iodine (I₂) being liberated
• This shows chlorine is more reactive than iodine

$2KI(aq) + Cl_2(aq) \rightarrow 2KCl(aq) + I_2(aq)$

Hydrogen Displacement

Non-metals can also displace hydrogen from compounds:

$CH_4(g) + Cl_2(g) \rightarrow CH_3Cl(g) + HCl(g)$

In sunlight, chlorine displaces hydrogen from methane, producing chloromethane and hydrogen chloride.

Oxygen (O₂)

• Strong oxidizing agent
• Supports combustion
• Oxidizes metals: $2Mg + O_2 \rightarrow 2MgO$

Chlorine (Cl₂)

• Greenish-yellow gas with pungent smell
• Strong oxidizing and disinfecting agent
• Used to treat water in Dar es Salaam and Arusha water treatment plants

Sulphur Dioxide (SO₂)

• Bleaching agent for dried flowers and fruits
• Reduces coloured dyes while being oxidized to SO₃
• Preservative for dried fish (traditional method in coastal Tanzania)

Ammonia (NH₃)

• Can act as reducing agent in some reactions
• Forms white smoke with HCl gas: $NH_3 + HCl \rightarrow NH_4Cl$

Carbon Dioxide (CO₂)

• Does not support combustion (used in fire extinguishers)
• Can oxidize in certain industrial processes

• Non-metals act as oxidizing agents by accepting electrons
• Displacement reactions occur when a more reactive non-metal displaces a less reactive one
• The halogen reactivity series: F₂ > Cl₂ > Br₂ > I₂
• Visible changes (colour changes, gas evolution) indicate displacement reactions have occurred

In Tanzania, chlorine is used in water treatment plants across cities like Mwanza and Dodoma to kill harmful bacteria — this relies on chlorine's strong oxidizing property. Additionally, traditional preservation of dried fish along the coast uses sulphur dioxide, which acts as a bleaching agent and preservative by inhibiting bacterial growth through oxidation.