Question

Describe an activity to show that blue copper sulphate crystal contains water of crystallisation

Answer 1

$\large\sf\bullet {\purple{\;Aim}}$

To show that copper sulphate crystals contain water of crystallisation.

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$\large\sf\bullet {\pink{\;Apparatus \:required}}$

➝ A dry boiling tube.

➝ A bunsen burner.

➝ A pair of tongs.

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$\large\sf\bullet{\orange{\; Procedure}}$

Take a few grams of copper sulphate crystals (blue colour) in the boiling tube. Make sure the tube is dry.

Heat the boiling tube using the bunsen burner. Hold the boiling tube using the tongs. You can notice that the blue colour of copper sulphate crystals fades away and finally, it becomes white.

You can also notice water droplets in the boiling tube which came out of nowhere.

Now, add 2-3 drops of water on the sample of copper sulphate obtained after heating.

You can find that, the copper sulphate crystals turned blue again when water is added.

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$\large\sf\bullet{\green{\; Observations}}$

Upon heating, the blue colour of copper sulphate crystals started fading away and it turned white.

Upon adding water, the white coloured copper sulphate turns blue again.

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$\large\sf\bullet{\red{\; Conclusions}}$

Copper sulphate crystals which seem to be dry contain water of crystallisation.

When heated, this water is removed from the crystals and the salt turns white.

When moistened again, the crystals gains the water of crystallisation and the colour of the crystals reappears.

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Answer 2

AIM - To determine the water of crystallization.

Materials we need - copper sulphate crystals, test tube holder, burner, boiling tube.

Procedure - ★ heat few crystals of copper sulphate in a dry boiling tube.

★we will observe that on heating blue crystals of copper sulphate, it becomes colourless and few drops of water are seen on the test tube.

★ then, on adding few drops of water to the heated copper sulphate, the blue colour of copper sulphate reappears.

the water of crystallisation is the fixed number of water molecules present in one formula unit of salt.