Why does effervescence when the Group 2 anion precipitate is acidified imply the presence of (CO3)2- ?
Because CO2 is the gas evolved and carbonates emit CO2 when treated with an acid.
Well, it's probably because the (CO3)2- ion is a real party animal. When it gets acidified, it starts to feel a little acidic hangover and gets all fizzy, causing effervescence! So, if you see things getting all bubbly, it's a good sign that those lively (CO3)2- ions are around, ready to bring the party to your test tube. Just don't forget to invite the other ions too, they might get jealous!
Effervescence when the Group 2 anion precipitate is acidified implies the presence of (CO3)2- due to the following chemical reaction:
1. Group 2 cations (e.g., Ca2+, Mg2+, etc.) can form insoluble carbonates (e.g., CaCO3, MgCO3, etc.) in basic solutions. These carbonates are often white precipitates.
2. When acid is added to the precipitate, it reacts with the carbonate ion, resulting in the formation of carbon dioxide gas (CO2), water (H2O), and a soluble salt.
CO3^2- + 2H+ -> CO2 + H2O
3. The formation of carbon dioxide gas leads to the effervescence or the production of bubbles.
Therefore, the observation of effervescence when the Group 2 anion precipitate is acidified indicates the presence of carbonate ions (CO3)2-.
Effervescence refers to the formation of bubbles or gas when a substance reacts with an acid. In the case of Group 2 anions, when the precipitate formed by these ions is acidified and effervescence occurs, it suggests the presence of carbonate ions (CO3^2-).
To understand why this happens, we need to consider the chemistry involved. Group 2 anions, specifically ions like carbonate (CO3^2-), can form precipitates with Group 2 cations such as calcium (Ca^2+), strontium (Sr^2+), or barium (Ba^2+). These precipitates are insoluble in water and usually appear as a white solid.
When an acidic solution, such as hydrochloric acid (HCl), is added to the precipitate, it reacts with the carbonate ions in the following reaction:
CO3^2- + 2H+ → CO2 + H2O
This reaction results in the formation of carbon dioxide gas (CO2) and water (H2O). The release of carbon dioxide gas causes effervescence, observable as bubbles.
Hence, the presence of effervescence when the Group 2 anion precipitate is acidified implies the existence of carbonate ions (CO3^2-) in the original sample.