Which of the following ores is in the form of sulphide?

What are the constituent elements of Magnalium?

Which method is used for the purification of semiconductor metals?

What is the melting point of sulfur (in $K$)?

What happens when:
$(i)$ $A$ piece of calcium is dropped in water.
$(ii)$ Sodium is kept exposed in air.
$(iii)$ Iron nail is dipped in copper sulphate solution.
$(iv)$ Potassium is dropped in cold water.
$(v)$ Carbon dioxide is compressed in water at high pressure.
Give chemical equations involved in all the above reactions and balance them.

What happens when calcium is treated with water?