GCSE Chemistry - Electrolysis Part 3 - Aqueous Solutions #42

Summary

This video explains the process of electrolysis, focusing on how it works in aqueous solutions. Electrolysis involves splitting compounds into elements by passing an electric current through an electrolyte, where ions must be free to move. For soluble compounds like copper sulfate and sodium chloride, dissolving them in water creates the electrolyte. The video details how ions react at the positive anode and negative cathode, explaining the rules for which ions are discharged based on reactivity. Examples include copper sulfate, where copper and hydroxide ions are discharged, and sodium chloride, where hydrogen and chloride ions are released.

Takeaways

• ⚡ Electrolysis splits compounds into their elements by passing an electric current through an electrolyte.
• 💧 Ions in an electrolyte must be free to move, meaning insoluble compounds need to be molten, while soluble compounds can dissolve in water.
• 📋 In electrolysis experiments, a beaker with electrolyte, two electrodes (anode and cathode), and a power supply are required.
• 🧲 Positive ions move to the negative cathode, while negative ions move to the positive anode.
• ⚖️ At the cathode, the ion of the least reactive element is discharged. Hydrogen will be discharged if it's more reactive than the metal ion present.
• 🔬 In aqueous solutions, ions from both the dissolved compound and water are present, including hydrogen and hydroxide ions.
• 🔋 At the anode, halide ions (if present) are discharged; otherwise, hydroxide ions are discharged, forming oxygen and water.
• 🔧 In the electrolysis of copper sulfate solution, copper ions are discharged at the cathode, forming solid copper, while hydroxide ions discharge at the anode, forming oxygen and water.
• 🌡️ The process at normal temperatures causes solid copper to accumulate around the cathode.
• 🧪 In the electrolysis of aqueous sodium chloride, hydrogen ions discharge at the cathode to form hydrogen gas, while chloride ions discharge at the anode to form chlorine gas.

Q & A

What is the purpose of electrolysis in chemistry?

Electrolysis is used to split compounds into their constituent elements by passing an electric current through an electrolyte.

Why is it necessary for the ions in an electrolyte to be free to move during electrolysis?

For electrolysis to work, ions must be free to move so they can migrate to the respective electrodes, allowing the process of electrolysis to occur.

What must be done to metal oxides for them to participate in electrolysis?

Most metal oxides are insoluble, so they need to be melted into a molten liquid to allow their ions to move freely and participate in electrolysis.

How are soluble compounds like copper sulfate prepared for electrolysis?

Soluble compounds like copper sulfate can be dissolved in water to create an electrolyte for the electrolysis process.

What components are required to set up an electrolysis experiment?

An electrolysis setup requires a beaker with electrolyte, two electrodes (a positive anode and a negative cathode), a wire connecting the electrodes, and a power supply.

How do you determine which ions will be discharged at the cathode in an aqueous solution?

At the cathode, the ion of the least reactive element will be discharged. This can be determined by referring to the reactivity series.

What happens at the anode during the electrolysis of aqueous solutions?

At the anode, negative ions from the electrolyte are attracted. If a halide ion is present, it will be discharged. If no halides are present, hydroxide ions from water will be discharged.

Why are copper ions discharged instead of hydrogen ions during the electrolysis of copper sulfate solution?

Copper ions are discharged at the cathode because copper is less reactive than hydrogen, according to the reactivity series.

What are the products formed at the cathode and anode during the electrolysis of copper sulfate solution?

At the cathode, pure copper is deposited as copper ions gain electrons. At the anode, hydroxide ions are discharged, producing oxygen and water.

What happens at the anode and cathode during the electrolysis of sodium chloride solution?

In the electrolysis of sodium chloride solution, hydrogen ions are discharged at the cathode, forming hydrogen gas. Chloride ions are discharged at the anode, producing chlorine gas.