Solve this:

​Q9. Which among the following changes are exothermic or ectothermic in nature?

          (a) Decomposition of ferrous sulphate

          (b) Dilution of sulphuric acid

          (c) Dissolution of sodium hydroxide in water

          (d) Dissolution of ammonium chloride in water


Q10. Why do fire flies glow at night?


Q11. Why the solution of silver nitrate becomes blue in colour after some time when copper turnings are added to it?


Q12. Ferrous sulphate decomposes with the evolution of a gas having a characteristic odour of burning sulphur. Write the chemical reaction involved and identify the type of reaction.