No mehnat bekar ho jayegi.
To start with, an interesting info, carbonates of Hg2+(not hg2 2+),Zn,Mg,Hg,Cu don't even exist naturally. I mean not like we study generally . They all exist as basic carboantes. The reason has to do sometthing wirh pressure(which i didn't quite understand) of H20 and great hydration enthalpies of therse metals.
For ex. this is what given in wiki page of CuCO3
The terms "copper carbonate", "copper(II) carbonate", and "cupric carbonate" almost always refer (even in chemistry texts) to a basic copper carbonate (or copper(II) carbonate hydroxide), such as Cu2(OH)2CO3 (which occurs naturally as the mineral malachite) or Cu3(OH)2(CO3)2 (azurite). For this reason, the qualifier neutral may be used instead of "basic" to refer specifically to CuCO3
The stability of dry CuCO3 depends critically on the partial pressure of carbon dioxide (pCO2). It is stable for months in dry air, but decomposes slowly into CuO and CO2 if pCO2 is less than 0.11 atm.
In the presence of water or moist air at 25 °C, CuCO
3 is stable only for pCO2 above 4.57 atmospheres and pH between about 4 and 8. Below that partial pressure, it reacts with water to form a basic carbonate (azurite, Cu3(CO3)2(OH)2).3 CuCO3H2O → Cu3(CO3)2(OH)2 + CO2
In highly basic solutions, the complex anion Cu(CO
3)22− is formed instead.
The solubility product of the true copper(II) carbonate was measured by Reiterer and others as pKso = 11.45 ± 0.10 at 25 °C.
Here is a table which confirms the same