Perform the following reactions and classifying them as physical or chemical changes: a) Iron with copper sulphate solution in water b) Burning of magnesium ribbon in air c) Zinc with dilute sulphuric acid d) Heating of copper sulphate crystals e) Sodium sulphate with barium chloride in the form of their solutions in water.

A. when an iron nail is dipped in copper sulphate, a brown coating of copper is formed on the surface of the iron and the colour of copper sulphate solution changes from blue to light green. this reaction shows that iron is more reactive than copper as it displaces copper from its solution and iron passes into solution as Fe{||} ions and ferrous sulphate solution is formed. its a physical change as it would not change into a completely new substance with new properties.

Explanation:

a 20-cm-long, cylindrical graphite (pure carbon) rod is inserted into an oxidizing atmosphere at 1145 k and 1.013 x 105 pa pressure. the oxidizing process is limited by the diffu- sion of oxygen counterflow to the carbon monoxide that is formed on the cylindrical surface.

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.