Pure copper sulphate can be obtained from an impure sample by the process of:

Options

A. evaporation
B. fractional distillation
C. centrifugation
D. crystallisation

Answer

To obtain pure copper sulfate from an impure sample, we can use the process of crystallization. Here’s a step-by-step breakdown of how this process works:

### Step-by-Step Solution:

1. **Dissolve the Impure Sample**: Start by dissolving the impure copper sulfate in a suitable solvent, typically water. This will allow the soluble copper sulfate to enter the solution while leaving behind any insoluble impurities.

2. **Heat the Solution**: Gently heat the solution to help dissolve any remaining impurities and to increase the solubility of copper sulfate. This step is crucial as it ensures that more copper sulfate can be dissolved.

3. **Filter the Solution**: Once the solution is heated and all soluble copper sulfate is dissolved, filter the solution to remove any insoluble impurities. This can be done using filter paper and a funnel.

4. **Cool the Solution**: After filtration, allow the solution to cool slowly. As it cools, the solubility of copper sulfate decreases, leading to the formation of crystals.

5. **Crystallization**: As the solution continues to cool, pure copper sulfate crystals will begin to form. This occurs because the dissolved copper sulfate is less soluble at lower temperatures, causing it to precipitate out of the solution.

6. **Collect the Crystals**: Once the crystals have formed, they can be collected by filtration. Rinse the crystals with a small amount of cold solvent to remove any adhering impurities.

7. **Dry the Crystals**: Finally, dry the collected crystals to obtain pure copper sulfate.

### Final Answer:
The correct process to obtain pure copper sulfate from an impure sample is **crystallization**.

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