Write two observations for the following chemical reaction:
$(a)$ Dilute sulphuric acid is poured over zinc granules.

When sulfur dioxide gas is passed through lime water,which insoluble substance is formed that turns the solution milky?

On heating blue coloured powder of copper $(II)$ nitrate in a boiling tube,copper oxide (black),oxygen gas and a brown gas $X$ is formed.
$(a)$ Write a balanced chemical equation of the reaction.
$(b)$ Identify the brown gas $X$ evolved.

Which among the following statement$(s)$ is(are) true? Exposure of silver chloride to sunlight for a long duration turns grey due to:
$(i)$ The formation of silver by decomposition of silver chloride
$(ii)$ Sublimation of silver chloride
$(iii)$ Decomposition of chlorine gas from silver chloride
$(iv)$ Oxidation of silver chloride

Write one equation each for decomposition reactions where energy is supplied in the form of heat,light,or electricity.

Write the chemical equation of the reaction with an example in which a change in colour takes place.