Making Salts - GCSE Science Required Practical

Summary

In this video, we demonstrate the process of preparing dry copper sulfate crystals through the neutralization of sulfuric acid with copper oxide. After carefully measuring and heating the acid, copper oxide is added in excess to ensure complete neutralization. The resulting blue copper sulfate solution is then filtered to remove unreacted copper oxide. To obtain pure dry crystals, the solution is gently heated using a steam bath to evaporate the water. Finally, the copper sulfate crystals are scraped out, providing a clean sample of the desired salt.

Takeaways

• 😀 Safety first: Always wear goggles when handling strong acids like sulfuric acid to protect your eyes.
• 😀 Copper oxide is a solid base used in this experiment to neutralize sulfuric acid and form copper sulfate.
• 😀 Neutralization reactions involve an acid and a base reacting to form a salt and water.
• 😀 The reaction between sulfuric acid and copper oxide results in the formation of copper sulfate, a soluble salt.
• 😀 To speed up the reaction, gentle heating is applied to the sulfuric acid using a Bunsen burner.
• 😀 An excess of copper oxide is added to ensure all the sulfuric acid reacts and is neutralized.
• 😀 The solution turns blue as the copper oxide reacts and dissolves, indicating the formation of copper sulfate.
• 😀 Unreacted copper oxide, which is black and insoluble, needs to be removed by filtration.
• 😀 Filtration is done using filter paper to separate the solid copper oxide from the blue copper sulfate solution.
• 😀 To obtain pure dry copper sulfate crystals, the water is evaporated gently using a steam bath instead of direct heating.
• 😀 After the water has evaporated, pure copper sulfate crystals are scraped from the evaporating dish, completing the process.

Q & A

What safety precautions should be taken when handling sulfuric acid?

Always wear goggles to protect your eyes from splashes, as sulfuric acid is a strong and potentially dangerous substance. Additionally, handle the acid carefully to avoid contact with skin or clothing.

Why is copper oxide used in this experiment?

Copper oxide is used because it is a base that reacts with sulfuric acid in a neutralization reaction, producing copper sulfate. It is a solid base that is not an alkali, but still capable of neutralizing an acid.

How do you know when you’ve added enough copper oxide?

You know you’ve added enough copper oxide when the solution turns blue, indicating that the acid has been neutralized. If some black copper oxide remains unreacted in the solution, it means you have added excess base.

What happens if you don’t add enough copper oxide to neutralize all the acid?

If enough copper oxide is not added, some acid will remain unneutralized in the solution, and the reaction will not be complete, which could affect the purity of the final copper sulfate crystals.

Why is filtering necessary in this experiment?

Filtering is necessary to remove any unreacted copper oxide from the copper sulfate solution. Since copper oxide is insoluble, it will be left behind during filtration, ensuring only the pure copper sulfate solution is retained.

What is the purpose of using a steam bath to heat the solution instead of directly heating it with a Bunsen burner?

A steam bath is used to gently heat the solution and prevent the copper sulfate from decomposing. Direct heating over a Bunsen burner could break down the copper sulfate, releasing harmful gases, so the steam bath offers a safer alternative.

What is the final product of this experiment?

The final product of this experiment is dry copper sulfate crystals. After evaporating the water from the filtered copper sulfate solution, the crystals are collected and are pure and dry.

Why is it important to add excess copper oxide in the neutralization step?

Adding excess copper oxide ensures that all the sulfuric acid is neutralized. This guarantees the formation of the maximum amount of copper sulfate, as any unreacted acid would prevent the complete reaction.

What should be done with the black copper oxide left after the reaction?

The black copper oxide, which is unreacted, should be removed through filtration. It is insoluble in the solution and must be separated to ensure the purity of the copper sulfate solution.

How can you tell when the evaporation process is complete?

You can tell the evaporation process is complete when no more water is visible in the evaporating basin, and dry, solid copper sulfate crystals are left behind.