Which of the following substances is hygroscopic?

Which method,other than the Contact process,is used for the production of sulfuric acid?

Give reasons for the following:
$(i)$ Ionic compounds have high melting and boiling points.
$(ii)$ Ionic compounds are soluble in water.
$(iii)$ Ionic compounds are solid and somewhat hard.
$(iv)$ Ionic compounds conduct electricity in the molten state.
$(v)$ Metals have a tendency to lose electrons.

What is the main component of natural gas?

What is an ore of aluminium?

Why are sulphide and carbonate ores converted into oxides?