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Table of Contents
Aim
To perform and observe the following reactions and classify them into:
Combination reaction: Action of water on quick lime.
Decomposition reaction: Action of heat on ferrous sulphate crystals.
Displacement reaction: Iron nails, kept in copper sulphate solution.
Double displacement reaction: Reaction between sodium sulphate and barium chloride solutions.
Materials Required
A beaker, four test tubes, a test tube holder, tongs, a test tube stand, a dropper, a piece of sandpaper and a bunsen burner.
Chemicals required: A small piece of quick lime, ferrous sulphate crystals, iron nails (clean and unrusted), copper sulphate solution, sodium sulphate solution, barium chloride solution and distilled water.
Procedure
1) Combination Reaction:
Experiment: Take a clean beaker, keep a small piece of lime in it and add water drop by drop into the beaker.
Observation: Reaction occurs with a crackling sound and steamy vapours are released. The beaker becomes hot.
Inference: An exothermic and combination reaction occurs.
Equation: (Only on the white page) [Quick lime → Quicklime]
2) Decomposition Reaction:
Experiment: Take a clean and dry test tube, and add a few crystals of ferrous sulphate. Fix it on a test tube holder. Heat the test tube on the burner, keeping the mouth of the test tube away from your face. Waft the gas released to smell.
Observation: The green crystals become reddish-brown, tiny droplets of water are settled near the neck of the test tube and a colourless gas with a choking smell is evolved.
Inference: Iron sulphate (green) crystals decompose due to heat. The water of crystallisation is collected in the test tube. It is a decomposition reaction.
Equation: (Only on the white page) [Dihydrogen Monoxide is in liquid state]
3) Displacement Reaction:
Experiment: Take a clean test tube, and add 2-3 mL of copper sulphate solution to it. Place an iron nail cleaned with sandpaper in it. Keep it on the test tube stand and observe the changes for about 30 minutes.
Observation: The blue colour of copper sulphate slowly fades away. The iron nail gets a deposit of reddish-brown colour. The blue colour of the solution changes to green.
Inference: Iron metal is more reactive than copper, so displaces it to form an iron sulphate solution. It is a displacement reaction and a reddish-brown deposit of copper is formed on the iron nail.
Equation: (Only on the white page) [You can interchange the reactants' positions]
4) Double Displacement Reaction:
Experiment: In a clean test tube, take sodium sulphate solution, to this, add barium chloride solution. Shake the contents and observe.
Observation: Both sodium sulphate and barium chloride solutions are colourless. On mixing together a white precipitate is formed.
Inference: The white insoluble precipitate of barium sulphate is formed. It is a double displacement reaction.
Equation: (Only on the white page)
Precautions
Do not touch quick lime with your hands, use tongs.
Mixing of quick lime and water releases a large amount of heat, so add water drop by drop and use a borosil beaker.
For heating, use hard glass tubes.
Never inhale any gas, just waft the gas.
Do not touch any chemicals with your hands.
Keep the mouth of the test tube away from your face while heating.
The iron nails must be cleaned properly by using sandpaper before dipping them in copper sulphate solution.
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