What is the percentage of sulfur used in vulcanized rubber for battery casings (in $\%$)?

Give reasons for the following:
$(i)$ Gold and platinum are used in jewellery.
$(ii)$ Copper cannot displace hydrogen from dilute acids.
$(iii)$ Stainless steel does not rust easily.
$(iv)$ Metals can be given different shapes according to our needs.
$(v)$ Zinc does not give hydrogen gas on reacting with $HNO_3$.

What happens when a piece of
$(a)$ zinc metal is added to copper sulphate solution?
$(b)$ aluminium metal is added to dilute hydrochloric acid?
$(c)$ silver metal is added to copper sulphate solution?
Also,write the balanced chemical equation if the reaction occurs.

Write chemical equations for the reactions taking place when:
$(i)$ iron is strongly heated in air.
$(ii)$ lead carbonate is calcined.
$(iii)$ chromium oxide $(Cr_{2}O_{3})$ is heated with aluminium powder.

$A, B$ and $C$ are three elements which undergo chemical reactions according to the following equations:
$A_{2}O_{3} + 2B \rightarrow B_{2}O_{3} + 2A$
$3CSO_{4} + 2B \rightarrow B_{2}(SO_{4})_{3} + 3C$
$3CO + 2A \rightarrow A_{2}O_{3} + 3C$
Answer the following questions with reasons:
$(a)$ Which element is the most reactive?
$(b)$ Which element is the least reactive?
$(c)$ What is the type of reactions listed above?

Identify the elements with the following properties and arrange them in increasing order of their reactivity:
$(a)$ An element which is a soft and reactive metal.
$(b)$ The metal which is an important constituent of limestone.
$(c)$ The metal which exists in a liquid state at room temperature.