PENENTUAN REAKSI REDUKSI DAN OKSIDASI PADA SEL ELEKTROLISIS

Summary

This video explains the principles of electrolysis, focusing on the reactions at the cathode and anode. It covers how reduction and oxidation occur depending on the type of electrolyte and electrode used. Key concepts include the reduction of water at the cathode for active metal solutions, the formation of solid metals from cations in molten solutions, and oxidation of water or anions at the anode. Practical examples, including NaCl and ZnSO4 solutions with platinum and copper electrodes, help illustrate these concepts. The video also discusses how gas formation at the cathode and anode varies based on the chemical nature of the electrolyte.

Takeaways

• 😀 Electrolysis involves electrodes, electrolyte solution, and a power source like a battery.
• 😀 The two electrodes in electrolysis are the cathode (reduction) and anode (oxidation).
• 😀 The cathode undergoes reduction reactions, while the anode undergoes oxidation reactions.
• 😀 Electrolyte solutions consist of cations and anions, like Na+ and Cl- in NaCl or Cu2+ and SO4 2- in CuSO4.
• 😀 The type of cation in the electrolyte determines the reduction reaction at the cathode.
• 😀 For active metals (Group 1A, 2A, aluminum, and manganese), water is reduced at the cathode rather than the metal cation.
• 😀 When cations are from transition metals, such as Cu2+, they undergo reduction at the cathode, forming solid metal.
• 😀 The type of anion in the electrolyte and the electrode material determines the oxidation reaction at the anode.
• 😀 Inert electrodes (e.g., platinum, graphite) lead to oxidation of water at the anode if the anions are from acids or are oxide anions.
• 😀 For halide anions (e.g., Cl-, Br-), oxidation at the anode produces halogen gas (e.g., Cl2, Br2).
• 😀 When the anode is made of a transition metal (like copper), the metal itself is oxidized into its cation form at the anode.

Q & A

What are the main components of an electrolytic cell?

An electrolytic cell consists of electrodes, an electrolyte solution, and a power source such as a battery. The electrodes are typically made of metals and include a cathode (where reduction occurs) and an anode (where oxidation occurs). The electrolyte contains cations and anions, which participate in the reactions.

What occurs at the cathode in an electrolytic cell?

At the cathode, reduction reactions occur. The cations in the electrolyte are reduced by gaining electrons. For example, in the case of aqueous solutions of alkali metals or alkaline earth metals, water is typically reduced to form hydroxide ions and hydrogen gas.

What is the general equation for the reduction of water at the cathode?

The general equation for the reduction of water at the cathode is: 2H2O + 2e⁻ → 2OH⁻ + H2.

How do you determine the reduction reaction at the cathode?

To determine the reduction reaction at the cathode, you must consider the type of cation in the electrolyte. If the cation is from a highly active metal, water is more likely to be reduced instead of the cation. For other cases, the cation itself will be reduced to form the metal.

What occurs at the anode in an electrolytic cell?

At the anode, oxidation reactions occur. Anions in the electrolyte are oxidized by losing electrons. If the anode is inert (like platinum or carbon), the oxidation reaction usually involves water, forming oxygen gas and protons.

What is the general equation for the oxidation of water at the anode?

The general equation for the oxidation of water at the anode is: 2H2O → 4H⁺ + O2 + 4e⁻.

How do you determine the oxidation reaction at the anode?

The oxidation reaction at the anode depends on the type of anode and the anion in the electrolyte. If the anion is a halide (like Cl⁻), it will be oxidized. If the anion is from an acid oxide (like SO4²⁻), water will be oxidized to produce oxygen gas.

What happens when an inert electrode like platinum or carbon is used at the anode?

When an inert electrode such as platinum or carbon is used, oxidation typically involves the anion in the electrolyte or water. For example, if the anion is chloride (Cl⁻), chlorine gas will be produced. If the anion is sulfate (SO4²⁻), water will be oxidized to produce oxygen gas.

What happens at the anode if the electrode is not inert?

If the anode is made of a reactive metal (such as copper), the metal itself undergoes oxidation, breaking down into metal ions. For example, if copper is used, the oxidation reaction would be: Cu → Cu²⁺ + 2e⁻.

How does the type of electrolyte affect the reactions in electrolysis?

The type of electrolyte determines which ions are available to undergo reduction at the cathode and oxidation at the anode. For example, in NaCl solution, Na⁺ ions are available to be reduced at the cathode, and Cl⁻ ions are available to be oxidized at the anode. In CuSO4 solution, Cu²⁺ ions are reduced at the cathode, while water is typically oxidized at the anode.