$NH_{3}$ is used in the preparation of nitric acid by $.....$ process.

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.
$(a)$ Identify the type of reaction.
$(b)$ What could be the $pH$ range of an aqueous solution of the gas $X$?

Crystals of copper sulphate are heated in a test tube for some time. What is the source of liquid droplets seen on the inner upper side of the test tube during the heating process?

$(a)$ Classify the following chemical reactions as exothermic or endothermic:
$(i)$ Electrolysis of water
$(ii)$ Burning of natural gas
$(iii)$ Decomposition of calcium carbonate
$(iv)$ Burning of magnesium ribbon in air.

What is the colour of $FeSO_{4} \cdot 7H_{2}O$ crystals? How does this colour change upon heating? Give the balanced chemical equation for the change.

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