8.5 Nuclear Reactions and Generation of Electricity

Nuclear Reaction:

• A nuclear reaction is a reaction where the nucleus of an element undergoes transformation.

• In a typical chemical reaction, electrons from the outermost layer of an atom or ion are exchanged, and the nucleus remains unaffected. In contrast, nuclear reactions involve changes to the nucleus of the atom, not the electrons.

• There are two main types of nuclear reactions: fission and fusion.

Nuclear Fission Reaction:

• Nuclear fission is the process where the nucleus of a heavy element (like uranium-235) is split into smaller nuclei, resulting in the release of energy.

• Example: When a neutron strikes the nucleus of uranium-235 (23/92U), the nucleus splits into two smaller nuclei: barium-141 (56/141Ba) and krypton-92 (36/92Kr). Along with this, three neutrons and a huge amount of energy are released.

• Fission Reaction:

• 23/92U + 1/0n → 56/141Ba + 36/92Kr + 3(1/0n) + Energy

Nuclear Fusion Reaction:

• Nuclear fusion is the process where nuclei of smaller elements combine to form a larger nucleus.

• Example: Hydrogen nuclei (1/1H) fuse to form helium (4/2He), releasing a huge amount of energy.

• Fusion Reaction:

• 1/1H + 1/1H → 4/2He + 1/0n + Energy

• Fusion is the basis for hydrogen bombs.

Nuclear Chain Reaction:

• A nuclear chain reaction occurs when the products of a nuclear reaction trigger additional reactions without the need for external energy input once it begins.

• In the example of uranium fission:

• When a neutron strikes a 23/92U nucleus, it splits and produces more neutrons.

• These neutrons can then strike other 23/92U nuclei, creating a self-sustaining chain of reactions.

• Controlling the pace of these reactions is complex, and this is the principle behind electricity generation in nuclear reactors.

Generation of Electricity:

• Nuclear reactors are used to control chain reactions that occur during nuclear fission.

• The fission reaction produces high-energy neutrons that cause further reactions. These neutrons accelerate smaller elements, creating a large amount of heat.

• This heat is used to produce steam, which drives turbines to generate electricity.

• In some reactor designs, the steam chamber is within the reactor itself.

• Nuclear power plants are operational in several countries worldwide. For example, Bangladesh is working on a nuclear power facility in Ruppoor, Pabna district, aiming to become self-sufficient in electricity.

Experiment: Galvanic Cell to Produce Electricity

Principle: A Galvanic cell generates electricity through a chemical reaction.

• A zinc rod is dipped in zinc sulfate (ZnSO4) solution and a copper rod in copper sulfate (CuSO4) solution. A salt bridge connects the two solutions.

Reactions:

• Anode (Zinc rod): Zinc atoms release electrons, turning into zinc ions (Zn → Zn²⁺ + 2e⁻).

• Cathode (Copper rod): Copper ions in solution accept electrons and become metallic copper (Cu²⁺ + 2e⁻ → Cu).

The flow of electrons between the two rods generates electricity.

Apparatus and Chemicals:

• Zinc rod, Copper rod, Zinc sulfate solution, Copper sulfate solution, Copper wire, LED bulb, Salt bridge (wet paper)

Procedure:

1. Place the zinc rod in the zinc sulfate solution and the copper rod in the copper sulfate solution in two separate beakers.

2. Connect the rods with the copper wire and place the wet paper as a salt bridge between the two solutions.

3. Connect the wire to the LED bulb. The bulb will light up as electrons flow through the wire.

4. As the reaction occurs, the zinc rod decays, and copper ions deposit on the copper rod.

Experiment: Dissolving Ammonium Chloride (NH4Cl) in Water

Principle: When ammonium chloride (NH4Cl) dissolves in water, it undergoes ionization, absorbing energy and cooling the solution, making the reaction endothermic.

Reaction:

• NH4Cl → NH4⁺ + Cl⁻

Apparatus and Chemicals:

• Beaker, Ammonium chloride (NH4Cl), Distilled water, Glass rod, Thermometer

Procedure:

1. Measure 50 grams of distilled water in a beaker.

2. Record the initial temperature of the water.

3. Add 10 grams of ammonium chloride to the water and stir with the glass rod.

4. Record the temperature once the ammonium chloride dissolves.

Result: The temperature of the water decreases, confirming that the dissolving of ammonium chloride is an endothermic reaction.

Experiment: Adding Lime (Calcium Oxide) to Water

Principle: Calcium oxide (lime) reacts with water, producing calcium hydroxide (Ca(OH)₂) and releasing heat, making the reaction exothermic.

Reaction:

• CaO + H₂O → Ca(OH)₂ + Heat

Apparatus and Chemicals:

• Beaker, Calcium oxide (CaO), Distilled water, Glass rod, Thermometer

Procedure:

1. Fill a beaker with distilled water.

2. Record the initial temperature of the water.

3. Add lime (calcium oxide) to the water and stir.

4. Record the new temperature after the reaction occurs.

Result: The temperature increases, indicating that the reaction is exothermic.