Question

aim material required procedure mehof observation of coppper sulphate heating

Answer 1

Lab Procedure: 

SI No.ExperimentObservationInference1 Take a piece of magnesium ribbon and rub it with  sand paper to remove dirt from its surface.It looks silvery white.Colour of magnesium metal is silvery white.2Hold the magnesium ribbon with the help of a pair of tongs, light the magnesium and collect the ash of burnt ribbon in a china dish.It burns brilliantly and a white ash is left behind.Magnesium burns in air to form Magnesium oxide (MgO).3 Take a moist red litmus paper and bring it in contact with the white ash of MgO.Red litmus paper turns blue.MgO is basic in nature.

Inferences:

Magnesium is a silvery white metal that burns in air and utilizes atmospheric oxygen from air to form magnesium oxide.



Magnesium oxide changes the colour of red litmus paper to blue. This reaction shows that magnesium oxide is basic in nature.The formation of magnesium oxide is a direct combination reaction of two elements: magnesium and oxygen. Magnesium oxide is entirely different from the reactants magnesium and oxygen. So, this reaction is a chemical change.

Precautions:

The surface of magnesium ribbon should be properly cleaned with sand paper.The white ash of magnesium oxide should not be touched.Magnesium ribbon should be held by a pair of tongs while burning it.It is better to use sun glasses to protect eyes from dazzling light of burning magnesium ribbon.

 

Reaction of Iron Nails with Copper Sulphate Solution in Water

Materials Required:



Lab Procedure:

Clean two iron nails of sufficient size by rubbing with sand paper so that their colour appears greyish.Take sufficient quantity of copper sulphate solution in two test tubes and fix one test tube in each stand.Tie one iron nail with a thread and hang it in one test tube so that it is completely immersed in copper sulphate solution. Tie the other end of the thread with the stand.Keep the other nail in a petri dish for comparison after the experiment.Keep the two test tubes undisturbed for about 15 min.After 15 min. remove the iron nail immersed in copper sulphate solution and put it in the petri dish.

Observations:

There is a brown coating on the iron nail which was dipped in the copper sulphate solution, whereas the iron nail placed in petri dish shows greyish colour of iron.The colour of the copper sulphate solution in which the iron nail was dipped turns light greenish, whereas the solution of copper sulphate in the other test tube does not change.

Inferences:

The brown coating on the iron nail shows that copper is deposited on the iron nail by displacing iron.The greenish colour of the solution in the test tube shows that Fe2+ ions are present in the solution.This shows that iron is more reactive than copper as Fe2+ ions have displaced Cu2+ ions from copper sulphate solution and form light greenish coloured ferrous sulphate solution.



This is a single displacement reaction in which copper has been displaced by iron from copper sulphate solution and a new compound, ferrous sulphate, is formed. So, this reaction is a chemical change. 

Precautions:

Clean the iron nails by rubbing them with sand paper to remove rust, dust or greasy surface.Keep the control experiment to compare the colour of iron nails and copper sulphate solution.Avoid touching copper sulphate solution or a nail dipped in copper sulphate solution. As copper sulphate is poisonous.

Heating of Copper Sulphate

Materials Required:



Lab Procedure:

Take a small amount of copper sulphate crystals in a dry boiling tube.Hold the boiling tube with a test tube holder.Heat the boiling tube over the flame of a burner first gently and then strongly.Observe the colour of copper sulphate crystals after heating for some time.Note the water droplets along the sides of the boiling tube.Remove the boiling tube from the flame and cool.Add 2-3 drops of water on the sample of copper sulphate obtained after heating.

Observations:

On heating, the colour of copper sulphate crystals changes from blue to white.There are water droplets on the walls of the boiling tube.On adding 2-3 drops of water white copper sulphate turns blue.

Inferences:



Copper sulphate crystals contain water of crystallisation (CuSO4.5H2O).On heating, hydrated copper sulphate loses its water molecule and forms white coloured anhydrous copper sulphate. On adding water anhydrous copper sulphate changes to hydrated copper sulphate.It is a reversible chemical change.

Precautions:

Keep the mouth of the test tube away from your face and also from other classmates.Always use test tube holder while heating the test tube.Take a small quantity of copper sulphate crystals.