Q.2 Rita placed a magnesium strip in blue copper sulphate solution in the test tube. Soon she observed that the blue coloured solution in the test tube has turned colourless and the magnesium strip has a coating of copper. A) Write the chelmical reaction for the following. [2] B) Among the four different types of chemical reactions
Answers
Answer:
Hold 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.