A metal ribbon 'X' burns in oxygen with a dazzling white flame forming a white ash 'Y'. The correct description of X, Y and the type of reaction is :

According to Activity 1.1, when a magnesium ribbon ($X$) is burnt in air, it reacts with oxygen to burn with a dazzling white flame and forms a white powder of magnesium oxide ($Y$). The chemical equation is $2Mg(s) + O_2(g) \longrightarrow 2MgO(s)$. Since two reactants ($Mg$ and $O_2$) combine to form a single product ($MgO$), this is a combination reaction.

• Option (a) is incorrect because calcium is not typically burned as a ribbon with a dazzling white flame in this standard activity, and the reaction is combination, not decomposition.
• Option (c) is incorrect because the metal is magnesium, not aluminium.
• Option (d) is incorrect because the reaction is highly exothermic, not endothermic, and the metal is magnesium.