Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it, as shown in figure below.

$(a)$ What will be the action of gas on

$(i)$ dry litmus paper ?

$(ii)$ moist litmus paper ?

$(b)$ Write a balanced chemical equation for the reaction taking place.

$(i)$ Write the electron-dot structures for sodium. oxygen and magnesium.

$(ii)$ Show the formation of $Na _{2} O$ and $MgO$ by the transfer of electrons.

$(iii)$ What are the ions present in these compounds ?

State two ways to prevent the rusting of iron.

Food cans are coated with tin and not with zinc because

Write equations for the reactions of

$(i)$ iron with steam

$(ii)$ calcium and potassium with water