Performing and observing the following reactions and classifying them into combination reaction decomposition reaction displacement reaction double displacement reaction action of water on quick lime action of heat on ferrous sulphate crystals 70 iron nails kept in copper sulphate solution reaction between sodium sulphate and barium chloride solutions show practical writing
Answers
Aim
To perform and observe the action of water on quicklime and classify the reaction.
Materials Required
Calcium oxide, water, beaker, glass rod, dropper, red litmus paper, test tube, filter paper, funnel.
Theory
Quicklime reacts with water to form calcium hydroxide. As in this reaction two substances – quicklime and water combine to form a new substance, therefore, this reaction is called combination reaction.
During this chemical change, heat is also released. Therefore, this is also an example of exothermic reaction.
Result
Two compounds, viz. quicklime and water combine to form calcium hydroxide. Therefore, this reaction is an example of combination reaction.
Precautions
Quicklime can cause severe burns, therefore, it should be handled with spatula.
As the reaction between quicklime and water is exothermic, water should be poured over quicklime slowly.
The filtrate collected should be clear.
EXPERIMENT 3(b)
Aim
To perform and observe the action of heat on crystals of ferrous sulphate and classify the reaction.
Material Required
Ferrous sulphate crystals, test tubes, test tube holder, blue limus paper.
Theory
The crystals of ferrous sulphate are green in colour. When these crystals are heated, following reaction takes place.
In this reaction, a single reactant breaks down to give simple products. Therefore, this is a decomposition reaction.
Ferrous sulphate crystals (FeS04.7H20) lose water when heated and the colour of crystals changes. It then decomposes to ferric oxide(Fe203), sulphur dioxide (S02) and sulphur trioxide (S03). Ferric oxide is solid while S02 and S03 are gases. Both S02 and S03 are acidic and hence, these gases turn the blue litmus red. Sulphur dioxide can reduce an acidified solution of potassium dichromate. This reaction can be utilised to confirm the presence of sulphur dioxide.
Resulst
On heating, ferrous sulphate decomposes to give ferric oxide, sulphur dioxide and sulphur trioxide. This decomposition reaction.
Precautions
While heating ferrous sulphate, keep the mouth of test tube away from you and your classmates.
EXPERIMENT 3(c)
Aim
To perform and observe the reaction of iron nails kept in copper sulphate solution and classify the reaction.
Materials Required
Iron nails, copper sulphate solution, test tubes, test tube stand, sandpaper and thread.
Theory
When an iron nail is immersed in copper sulphate solution, following reaction takes place:
In the above reaction, iron ions (Fe2+) being more reactive displaces copper ions (Cu2+) and a new compound ferrous sulphate is formed. This type of reactions is called displacement reaction.
Procedure
Take two iron nails and clean them by rubbing with sandpaper.
Take two test tubes and mark them as ‘A’ and ‘B’.
In each test tube, pour about 10 ml of copper sulphate solution.
Tie one iron nail with a thread and immerse this carefully in the copper sulphate solution in test tube A for about 20 minutes. Keep aside one nail for comparison.
After 20 minutes, take out the iron nail from the copper sulphate solution.
Compare the intensity of blue colour of copper sulphate solutions of both the test tubes ‘A’ and ‘B\
Also, compare the colour of iron nail dipped in copper sulphate solution with one kept aside.
Observations
The initial colour of copper sulphate solution was blue which after immersing iron nails turns to light green.
The initial colour of iron nail was grey. After immersing the nail into copper sulphate solution, a brown coating developed over it. Because of this coating iron nail appears reddish brown.
Result
On keeping the iron nails in copper sulphate solution, a displacement reaction takes place. In this displacement reaction, iron displaces copper and two new products ferrous sulphate and copper are formed.
Precautions
The iron nails should be cleaned by rubbing them with a sandpaper.
The test tube containing iron nails and copper sulphate solution should not be disturbed.
EXPERIMENT 3(d)
Aim
To perform and observe the reaction between sodium sulphate and barium chloride solutions and classify the reaction.
Materials Required
Sodium sulphate solution, barium chloride solution, test tubes, beaker.
Theory
When the solutions of sodium sulphate and barium chloride are mixed, a white precipitate of barium sulphate is formed. Chemical equation for this chemical change can be given as follows:
In this reaction, both sodium sulphate and barium chloride exchange ions. Hence, this type of reaction is called double displacement reaction.
Procedure
Take 5 ml of sodium sulphate solution in a test tube and mark it as ‘A’.
Take 5 ml of barium chloride solution in another test tube and mark it as ‘B’.
Mix the solutions of test tubes ‘A’ and ‘B’ in a beaker.
With the help of a clean glass rod, stir the mixture kept in beaker.
Record your observation.
Observation
On mixing the solutions of sodium sulphate and barium chloride, a white precipitate is formed.
Result
On mixing the solutions of sodium sulphate and barium chloride, a double displacement reaction takes place.
Answer:
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