Please solve this problem

Solubilities of carbonates and bicarbonates of alkali metals and alkaline earth metals increase down the group. 

Group-2 carbonates are sparingly soluble in water as their lattice energies are higher (it is due to increase in covalent nature).

so option D is correct Shib

sir please explain

wait..

video solution https://youtu.be/Kl6acJZCcZc

sir in this video they didn't told the reason

In the give metal bicarbonates, the anion (bicarbonate ion) is the same. Hence the solubility will depend on the size of cation. The size of Na+ ion is smaller than that of K+ ion. Hence sodium bicarbonate has high lattice energy and lower solubility than potassium bicarbonate.

CaCo3 is a strong ionic compound. Due to high electrostatic force of attraction the atoms are held so strongly together that you can not only break it easily but also cant dissole it. though CaCo3 decomposes in heat ,but it is insoluble in water in all conditions.

got it?

sir please explain

https://youtu.be/Kl6acJZCcZc check this shib

sir in this video they just told that which has highest and which has lowest solubility but didn't say the reason

Dear shib...solubility of bicarbonates is more than carbonates

And you know fajans rule....smaller the cation,larger the anion more the covalent character

and covalent character inversely proportional to solubility

between K+ and Na+...size of Na+ cation is smaller so it has more covalent charcter hence less solubility than khco3

so overall order becomes Khco3>Nahco3>caco3

now got this dear shib??