• Take one of the following sets X and Y of chemicals?X ? Y(i) Copper sulphate ? Sodium carbonate(ii) Barium chloride ? Sodium sulphate(iii) Lead nitrate ? Sodium chloride
• Prepare separately 95% solution of any one pair of substances listed under X and Y in water.
• Take little amount of solution of Y in a conical flask and some solution of X in an ignition tube.
• Hang the ignition tube in the flask carefully; see that the solutions do not get mixed.
• Put a cork on the flask as shown in figure.
• Weigh the flask with its contents carefully.
• Now tilt and swirl the flask, so that the solutions X and Y get mixed.
• Weigh again.
• What happens in the reaction flask?
• Do you think that a chemical reaction has taken place?
• Why should we put a cork on the mouth of the flask?
• Does the mass of the flask and its contents change?

Conical Flask Test Tube Solution X Solution Y Fig Ignition tube containing solution of X, dipped in a coical flask containing solution of Y.