[AdiDex]

Why CaCl₂ is more deliquescent than NaCl . I have no answer rather than it has more affinity towards water molecules . My teacher said that it is related to the vapor pressure .
This is seriously out of my reach . I tried to google but didn't find anything . Then I made a prediction . Like any other solids both of these have vapor pressure (Very tiny although) , so when they escape out from the lattice then around them there is water vapor so they attract them and get attached with them then they come back again , this is how they got water vapor on their surface . (second way is that Water vapor is around them , it get trapped in the lattice due to different affinity of different solids. But this reason is not related with vapor pressure , back to the first mechanism) .
Then I thought there should be basically two factors for different deliquescence nature .

1. If some solid is more volatile (Not so much like camphor, Just comparable eg. 1 torr and 0.5 torr)  , then the solid will have more of its molecule in gaseous phase , so greater the chance of getting attached with water vapor .
2. If some solid has greater lattice energy , then it should attract more water molecule in the gas phase (As it will be more unstable) .

So lattice energy of CaCl2 is higher . vapor pressure of NaCl at room temperature is seems to be lower than that of CaCl2 ^[1],[2] .

[1] Vapor pressure of CaCl₂ = 0.1 mm Hg , 13.3 Pa at 293K   --> http://www.chemicalbook.com/chemicalproductproperty_en_cb3465202.htm
[2]  Vapor pressure of NaCl at 865 K = 1 Torr = 133 Pa (But it is in molten state at this temperature) http://www.chemicalbook.com/ChemicalProductProperty_EN_CB4104636.htm

Can anybody suggest me am I on right track or not ??

[AWK]

https://www.britannica.com/science/deliquescence

[AdiDex]

I have read it already . It's suggest that what happens during Deliquescence , but doesn't tell why ..!! Either that teacher said something wrong or I am not getting his point.

[AdiDex]

Hello ?? Anybody ther...!!

[Borek]

No idea what your teacher might have on mind. Sure, the vapor pressure of everything (be it water or the salt itself) is somehow related to the properties of the salt and its affinity to water, but in no way it is the reason behind the effect.