Chlorine Preparation & Reactions

Introduction to Chlorine

Chlorine is a greenish-yellow gas at room temperature and is a member of the halogen group in the periodic table. It is highly reactive, especially with metals and hydrogen.

Industrial Preparation of Chlorine

Chlorine is primarily produced by the electrolysis of sodium chloride (NaCl) solution, known as brine. This process is called the Chlor-alkali process.

• Electrolysis of Brine: When an electric current is passed through brine, chlorine gas is produced at the anode, hydrogen gas at the cathode, and sodium hydroxide remains in solution.

Chemical Equation

The overall chemical equation for the electrolysis of brine is:

$$2NaCl(aq) + 2H_2O(l) \rightarrow 2NaOH(aq) + Cl_2(g) + H_2(g)$$

Reactions of Chlorine

Chlorine is a versatile element that participates in several types of chemical reactions:

• Halogenation: Chlorine can react with hydrocarbons to form chlorinated compounds. For example, with methane, it forms chloromethane.
• Reaction with Metals: Chlorine reacts with metals to form metal chlorides, such as sodium chloride (NaCl).
• Reaction with Hydrogen: Chlorine reacts with hydrogen to form hydrogen chloride (HCl), a hydrogen halide.

Example: Reaction with Hydrogen

When chlorine gas reacts with hydrogen gas, hydrogen chloride is formed:

$$Cl_2(g) + H_2(g) \rightarrow 2HCl(g)$$

Addition Reactions with Halogens

Chlorine, like other halogens, can undergo addition reactions with unsaturated hydrocarbons (alkenes and alkynes) to form dihalogenated compounds.

Example: Addition to Ethene

When chlorine is added to ethene, 1,2-dichloroethane is formed:

$$C_2H_4(g) + Cl_2(g) \rightarrow C_2H_4Cl_2(l)$$