What is formed when sulfur trioxide gas is absorbed in concentrated sulfuric acid?

Explain why calcium metal starts floating on the surface of water after reacting with it. Write the chemical equation for the reaction.

Provide one exception for each of the following general statements:
$(i)$ Metals are lustrous.
$(ii)$ Metals are solids at room temperature.
$(iii)$ Metals have high melting points.
$(iv)$ Non-metals are non-lustrous.
$(v)$ Non-metals are insulators or non-conductors of electricity.

What are the constituent elements of brass?

Which metal is the second most abundant metal found on Earth?

$(i)$ Define the term 'anode mud'. Name the electrode made of pure metal.
$(ii)$ Give the reactions taking place at cathode and at anode during the electrolytic refining of copper.