Illustrate an activity to show a double displacement reaction. Give the chemical equation of the reaction that takes place.

When a green iron salt is heated strongly, its colour finally changes to black and odour of burning sulphur is given out.
Write the balanced chemical equation for the reaction involved.

What is a redox reaction? Identify the substance oxidised and the substance reduced in the following reactions.
 ${\mathrm{Pb}}_3{\mathrm{O}}_4 + 8\mathrm{HCl} \to 3{\mathrm{PbCl}}_2 + {\mathrm{Cl}}_2 +4{\mathrm{H}}_2\mathrm{O}$

What is a redox reaction? Identify the substance oxidised and the substance reduced in the
following reactions.

$\mathrm{CuO} + {\mathrm{H}}_2\to \mathrm{Cu} + {\mathrm{H}}_2\mathrm{O}$

Define corrosion. Under what conditions do corrosion take place?