Sel Elektrolisis | Kimia SMA | Tetty Afianti

Summary

This chemistry lecture on electrolysis covers the principles of electrolysis cells, focusing on the roles of inert and non-inert electrodes. The instructor defines key concepts such as reduction at the cathode and oxidation at the anode, providing specific examples, including sodium nitrate and hydrochloric acid solutions. Various reactions are detailed, emphasizing the factors influencing each process. The lecture concludes with practice problems for students to solidify their understanding, along with encouragement to seek further resources for additional practice. Overall, it offers a comprehensive overview of electrolysis essential for chemistry students.

Takeaways

• 😀 Electrolysis involves the decomposition of an electrolyte using direct electric current.
• ⚡ The cathode is the negative electrode, while the anode is the positive electrode.
• 🔍 Remember the acronym 'KENAPE' to differentiate between electrodes: K for Cathode (negative) and A for Anode (positive).
• 💡 In electrolysis, there are two types of electrodes: inert electrodes (like platinum and carbon) and reactive electrodes.
• 🔄 Reactions at the cathode can involve the reduction of water or metal ions, depending on the electrolyte present.
• 🔺 Anode reactions can involve the oxidation of water or halide ions, influenced by the presence of acidic residues.
• 🧪 Example reactions include electrolysis of sodium nitrate, hydrochloric acid, and copper sulfate solutions.
• 📊 The importance of balancing electrons in the overall reaction is emphasized for accurate results.
• 🔗 The electrolysis of molten compounds, like magnesium chloride, follows similar principles but differs in the state of the electrolyte.
• 📚 Students are encouraged to practice additional exercises to reinforce their understanding of electrolysis reactions.

Q & A

What is the definition of an electrolytic cell?

An electrolytic cell is a system where an electrolyte is decomposed using direct current, resulting in the separation of its constituents.

What is the significance of the cathode and anode in an electrolytic cell?

The cathode is the negative electrode where reduction occurs, while the anode is the positive electrode where oxidation takes place.

How can one remember the functions of the cathode and anode?

A mnemonic to remember their functions is 'Kenape' (Cathode Negative, Anode Positive) for electrolytic cells and 'Kapan' (Cathode Positive, Anode Negative) for voltaic cells.

What types of electrodes are used in electrolysis?

There are two types of electrodes: inert electrodes, which do not participate in the reaction (e.g., platinum, gold, carbon), and non-inert electrodes, which do participate in the reaction.

What happens at the cathode when electrolyzing a solution of Group 1A metal?

When electrolyzing a solution with Group 1A metals, water is reduced at the cathode according to the reaction: 2 H2O + 2 e- → H2 + 2 OH-.

What is the reaction at the anode when there are residual acid ions?

If residual acid ions are present, the reaction at the anode is: 2 H2O → 4 H+ + O2 + 4 e-.

How do halide ions behave during electrolysis?

Halide ions are oxidized at the anode to form halogen gases, with the reaction: 2 X- → X2 + 2 e-.

What is the reaction at the cathode for copper(II) sulfate solution using an iron electrode?

The reaction at the cathode is: Cu2+ + 2 e- → Cu, resulting in the deposition of copper.

What is the outcome of electrolyzing magnesium chloride (MgCl2) with an inert electrode?

During the electrolysis of MgCl2, magnesium ions are reduced at the cathode to form magnesium metal, while chloride ions are oxidized at the anode to produce chlorine gas.

What should one do to balance the reactions during electrolysis?

To balance the reactions, ensure that the number of electrons lost in oxidation equals the number gained in reduction. Adjust the coefficients accordingly to achieve this balance.