GCSE Chemistry Revision "Required Practical 1: Making Soluble Salts"

Summary

This video tutorial provides a clear guide on how to create soluble salts, specifically focusing on the synthesis of copper sulfate using dilute sulfuric acid. The process involves reacting a solid copper oxide with the acid to produce a blue copper sulfate solution. Key steps include heating the acid, adding copper oxide until the solution is neutral, filtering out unreacted materials, and evaporating the solution to form pure copper sulfate crystals. This practical experiment is essential for exam preparation and understanding fundamental chemistry concepts.

Takeaways

• 😀 Salts are compounds consisting of positive and negative ions, with copper sulfate being an example of a soluble salt.
• 🧪 Copper sulfate contains the positive ion Cu²⁺, which can come from various sources, including metals and metal compounds.
• 🚫 Copper itself cannot react with dilute sulfuric acid to produce copper sulfate due to its low reactivity.
• ⚗️ To make a soluble salt like copper sulfate, you can use either a metal oxide (e.g., copper oxide) or a metal carbonate (e.g., copper carbonate).
• 💧 Dilute sulfuric acid is used to provide the negative sulfate ions (SO₄²⁻) needed for salt formation.
• 🔥 The process begins by heating the dilute sulfuric acid without boiling it, ensuring it doesn’t bubble over during the reaction.
• 🥄 Small amounts of copper oxide are added to the acid, and the solution is stirred until a blue color indicates the reaction is complete.
• 🧼 Any unreacted copper oxide, which is insoluble, is removed by filtration using a filter funnel and paper.
• 💨 To obtain pure copper sulfate crystals, the filtered solution is evaporated gently until about half remains.
• ⏳ After evaporation, the solution is left to cool for 24 hours to allow the formation of crystals, which are then dried.

Q & A

What is the primary goal of the video?

The primary goal of the video is to describe how to make a soluble salt using an acid, specifically focusing on the practical steps involved in making copper sulfate.

What are the key components of a salt?

Salts consist of a positive ion, which in this case is the copper ion (Cu²⁺), and a negative ion, which is the sulfate ion (SO₄²⁻) when using sulfuric acid.

What are the possible sources of the metal ion in salts?

The metal ion can come from the metal itself, a metal oxide, a metal hydroxide, or a metal carbonate.

Why can't copper sulfate be made by reacting copper with dilute sulfuric acid?

Copper cannot react with dilute sulfuric acid because it is not reactive enough to displace the hydrogen ions from the acid.

What is the first step in making copper sulfate?

The first step is to gently heat a fixed amount of dilute sulfuric acid until it is almost boiling, ensuring that it does not boil over.

What should you observe when copper oxide is added to the heated sulfuric acid?

You should observe the copper oxide reacting with the acid and seemingly disappearing, turning the solution blue, which indicates the formation of copper sulfate.

How can you determine when to stop adding copper oxide to the acid?

You should stop adding copper oxide when the solution turns clear blue, indicating that all the acid has reacted, and some unreacted copper oxide remains.

What is the purpose of filtering the solution after the reaction?

Filtering is done to remove any unreacted copper oxide, as it is insoluble and would contaminate the copper sulfate solution.

Describe the process of crystallizing copper sulfate from the solution.

To crystallize copper sulfate, the filtered solution is placed in an evaporating basin and gently heated over boiling water until about half of the solution remains. Then, it is left to cool for 24 hours to allow crystals to form.

What should you do with the copper sulfate crystals after they form?

After the crystals form, they should be scraped onto a paper towel and gently patted dry to obtain pure dry crystals of copper sulfate.