To create neutral salt crystals, specifically copper chloride, from copper oxide and hydrochloric acid, the process involves a chemical reaction followed by purification steps. According to the provided reference, the method to produce pure dry crystals of copper chloride from copper oxide and dilute hydrochloric acid is straightforward: add hydrochloric acid to copper oxide, filter the mixture, and allow the filtrate to evaporate to obtain pure crystals.
The Process: Turning Copper Oxide into Copper Chloride Crystals
This method leverages the reaction between a metal oxide (copper oxide) and an acid (hydrochloric acid) to form a salt (copper chloride) and water. The salt is then isolated in crystalline form.
Key Steps
The process can be broken down into three main stages, based on the reference:
- Reaction: Adding hydrochloric acid to copper oxide.
- Separation: Filtering the mixture.
- Crystallization: Allowing the filtrate to evaporate.
Let's look at each step in detail.
Step 1: Adding Hydrochloric Acid to Copper Oxide
- Action: Hydrochloric acid (typically used as a dilute solution in this type of preparation) is added to copper oxide.
- Purpose: Copper oxide is a base, and hydrochloric acid is an acid. When they react, they neutralize each other, forming the salt copper chloride and water. The chemical equation for this reaction is:
CuO (s) + 2HCl (aq) → CuCl₂ (aq) + H₂O (l) - Observation: As the reaction proceeds, the black solid copper oxide dissolves, and the solution turns blue-green, indicating the presence of copper(II) ions (Cu²⁺) in the copper chloride solution. You typically add the copper oxide in excess to ensure all the acid reacts.
Step 2: Filtering the Mixture
- Action: Once the reaction is complete (indicated by no more copper oxide reacting, leaving behind any excess solid), the mixture is filtered.
- Purpose: Filtering removes any unreacted solid copper oxide or other insoluble impurities from the solution. This step is crucial for obtaining pure crystals, as mentioned in the reference.
- Result: The liquid collected after filtering is called the filtrate. It is a clear blue-green solution containing the dissolved copper chloride and water.
Step 3: Allowing the Filtrate to Evaporate
- Action: The clear filtrate is then left to evaporate. This can be done slowly at room temperature or by gentle heating.
- Purpose: As the water evaporates, the concentration of dissolved copper chloride increases. Eventually, the solution becomes saturated and then supersaturated, causing the copper chloride to crystallize out of the solution.
- Result: As the water fully evaporates, pure, dry crystals of copper chloride are left behind.
Obtaining Pure, Dry Crystals
The method described ensures the crystals are both pure and dry.
- Purity: Filtration removes insoluble impurities. Using excess copper oxide helps ensure all the acid reacts, so no acid is left in the final solution.
- Dryness: Allowing all the water to evaporate yields dry crystals.
This process is a standard laboratory technique for preparing soluble salts from an insoluble base (like copper oxide) and an acid.
| Step | Action | Purpose |
|---|---|---|
| 1. Reaction | Add Hydrochloric Acid to Copper Oxide | Form Copper Chloride Salt and Water |
| 2. Separation | Filter the Mixture | Remove unreacted solids and impurities |
| 3. Crystallization | Evaporate the Filtrate | Obtain pure, dry Copper Chloride Crystals |
Following these steps, based directly on the provided reference, allows for the successful preparation of neutral salt crystals (copper chloride) from copper oxide and hydrochloric acid.
