Unlike other metal carbonates that usually decomposes into metal oxides liberating carbon dioxide, silver carbonate on heating decomposes into elemental silver liberating mixture of carbon dioxide and oxygen gas as :Ag2​CO3​(s)MW=276 g​⟶ Heat ​2Ag(s)+CO2​( g)+21​O2​( g)2×108=216 g​Hence, 2.76 g of Ag2​CO3​ on heating will give 276216​×2.76=2.16 gAg as residue.