4. Electrochemistry (Part 1) (1/3) (Cambridge IGCSE Chemistry 0620 for 2023, 2024 & 2025)

Summary

In this video, IGCC Study Budd covers the basics of electrochemistry, focusing on electrolysis. Electrolysis is the process of breaking down ionic compounds into their elements using electric current, either in molten or aqueous solutions. The video explains key components such as electrodes (cathode and anode) and how ions move during electrolysis. It highlights oxidation (loss of electrons) at the anode and reduction (gain of electrons) at the cathode, along with the mnemonic OIL RIG for remembering these concepts. The video also discusses ionic half-equations for understanding the electrolysis process.

Takeaways

• 📚 Electrolysis is the decomposition of an ionic compound in molten or aqueous form through the passage of electric current.
• ⚡ Electrolysis requires free ions to allow electricity to pass through the electrolyte.
• 🔌 An electrode is a conductor, often made of metal or graphite, that allows electric current to enter or exit the electrolyte.
• 💧 The electrolyte can be molten (liquid from heating) or aqueous (dissolved in water).
• 🔋 Cations are positively charged ions, while anions are negatively charged ions.
• ➖ The cathode is the negative electrode, attracting positive cations, while the anode is the positive electrode, attracting negative anions.
• 🔄 During electrolysis, cations move towards the cathode and gain electrons (reduction), while anions move towards the anode and lose electrons (oxidation).
• ⚖ Oxidation is the loss of electrons, and reduction is the gain of electrons, easily remembered by the acronym OIL RIG.
• 🧪 The products of electrolysis depend on the ions present in the electrolyte and their interactions at the electrodes.
• 📝 Ionic half-equations show the electron loss or gain during electrolysis, and it's essential to balance charges in these equations.

Q & A

What is electrolysis?

Electrolysis is the decomposition of an ionic compound when molten or in aqueous solution by the passage of an electric current.

Why must an ionic compound be molten or in aqueous solution for electrolysis?

In order for electrolysis to occur, the ionic compound must have free ions, which only happens when the compound is molten or dissolved in water, allowing electricity to pass through.

What is the function of an electrode in an electrolytic cell?

An electrode is a conductor, often made of metal or graphite, that allows electric current to flow in or out of the electrolyte during electrolysis.

What is the difference between a cation and an anion?

A cation is a positively charged ion that forms when an atom loses electrons, while an anion is a negatively charged ion that forms when an atom gains electrons.

What is the role of the cathode in electrolysis?

The cathode is the negative electrode that attracts positively charged cations. These cations gain electrons at the cathode, undergoing reduction.

What happens at the anode during electrolysis?

The anode is the positive electrode that attracts negatively charged anions. At the anode, these anions lose electrons, undergoing oxidation.

How can you remember which electrode is positive and which is negative?

You can remember that the cathode is negative because it attracts cations (which are positive), and the anode is positive because it attracts anions (which are negative).

What carries the electric charge in an electrolyte during electrolysis?

In the electrolyte, it is the ions that move and carry the electrical charge during electrolysis, whereas in the electrodes and wires, electrons carry the charge.

What is oxidation and reduction in the context of electrolysis?

Oxidation is the loss of electrons, which occurs at the anode, and reduction is the gain of electrons, which occurs at the cathode. This can be remembered by the mnemonic 'OIL RIG' (Oxidation Is Loss, Reduction Is Gain).

What are the half equations for the electrolysis of molten sodium chloride?

At the anode, 2 chloride ions (Cl⁻) lose 2 electrons to form chlorine gas (Cl₂). The equation is: 2Cl⁻ → Cl₂ + 2e⁻. At the cathode, sodium ions (Na⁺) gain an electron to form sodium metal (Na). The equation is: Na⁺ + e⁻ → Na.