List two observations which you record while burning magnesium in air.

Which of the following are combination reactions?
$(i)$ $2 KClO_{3} \xrightarrow{\text{Heat}} 2 KCl + 3O_{2}$
$(ii)$ $MgO + H_{2}O \longrightarrow Mg(OH)_{2}$
$(iii)$ $4 Al + 3O_{2} \longrightarrow 2 Al_{2}O_{3}$
$(iv)$ $Zn + FeSO_{4} \longrightarrow ZnSO_{4} + Fe$

Write a balanced chemical equation for each of the following reactions and also classify them.
$(a)$ Iron $(III)$ oxide on heating with carbon monoxide gas reacts to form solid iron and liberates carbon dioxide gas.
$(b)$ Hydrogen sulphide gas reacts with oxygen gas to form solid sulphur and liquid water.

Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved?
$(i)$ Displacement reaction
$(ii)$ Precipitation reaction
$(iii)$ Combination reaction
$(iv)$ Double displacement reaction

$2 \, g$ of ferrous sulphate crystals are heated in a boiling tube.
$(i)$ State the colour of ferrous sulphate crystals both before heating and after heating.
$(ii)$ Name the gases produced during heating.
$(iii)$ Write the chemical equation for the reaction.

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