Which gas is produced when a base reacts with a metal?

Which gas is released when acid reacts with metal carbonate or metal hydrogen carbonate?

Melittin present in the bite of honeybee is a polypeptide containing $......$ amino acids.

$(i)$ Name the products obtained in the chlor-alkali process.
$(ii)$ Name the gases liberated at the anode and at the cathode,respectively.
$(iii)$ Name the solution which is used as raw material in this process.

Write balanced chemical equations for the following:
$(i)$ Bleaching powder is kept open in air.
$(ii)$ Blue crystals of copper sulphate are heated.
$(iii)$ Chlorine gas is passed through dry slaked lime.

Which of the following statements is not correct?