Translate the following reactions into balanced chemical equations:
$(i)$ Manganese dioxide is heated with aluminium powder.
$(ii)$ Iron is treated with steam.

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 $X$?

Write one example for each of the decomposition reactions carried out with the help of:
$(i)$ electricity
$(ii)$ heat
$(iii)$ sunlight
Give balanced chemical equations in each case.

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.

$A$ magnesium ribbon is burnt in oxygen to give a white compound $X$ accompanied by emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen,it continues to burn and forms a compound $Y.$
$(a)$ Write the chemical formulae of $X$ and $Y.$
$(b)$ Write a balanced chemical equation,when $X$ is dissolved in water.

Observe the given figure and answer the following questions:
$(i)$ Write the complete balanced chemical equation for the reaction.
$(ii)$ Write the type of reaction involved.
$(iii)$ Is there any precipitate formed?
$(iv)$ If any precipitate is formed,write the colour of the precipitate.