(i) 2Mg + O2→ 2MgO + Light
3Mg + N2→ Mg3N2
(a) X is MgO; Y is Mg3N2
(b) MgO + H2O→ Mg(OH)2
(ii) Grapes when attached to the plants are living and therefore, their own immune system prevents fermentation. The microbes can grow in the plucked grapes and under anaerobic conditions these can be fermented. This is a chemical change.