In the presence of which catalyst is sulphur dioxide heated at high temperature to form sulphur trioxide?

Which mixture of two gases,taken in equal proportions in a gas jar,reacts in the presence of sunlight?

Give a reason why electrical wires are coated with plastic.

$(i)$ Explain the steps for extraction of copper from its sulphide ore. Write the balanced equations involved in the process.
$(ii)$ What is meant by refining of metals? Draw a diagram of electrolytic refining of copper and name the substances used as cathode, anode, and the electrolyte.

Which metal is available in the highest proportion on the earth's crust?

Of the three metals $X, Y$ and $Z$,$X$ reacts with cold water,$Y$ with hot water,and $Z$ with steam only. Identify $X, Y$ and $Z$ and also arrange them in the order of increasing reactivity.