Question

How is hydration energy dependent on lattice energy? Are they inversely proportional?

Answer 1

@chmvijay

Answer 2

if the higher the lattice energy then higher will be the hydration energy :) they are directly linked :)

Answer 3

irrespective to the sign of enthalpy i assume

Answer 4

But then how can some compounds have low lattice energy and high hydration energy?I believe that is the condition for solubility.

Answer 5

low lattice energy mean the ions can be formed very easily as called low hydration energy :)

Answer 6

Now that is confusing :O

Answer 7

Solubility depends on the decrease of enthalpy hydration and lattice enthalpy relative to each other, a substance is more soluble if the decrease in lattice enthalpy is more significant than the decrease in hydration enthalpy, which makes enthalpy solution to be more exothermic( more negative). Basically if a substance is said to hve high lattice enthalpy, then it means more energy is needed to break the ions to from gaseous ions, similarly in hydration enthalpy more energy is released out when the gaseous ions makes bonds with the water molecules which is an exothermic process. therefore they both should be directly related to each other if we dont tke the enthalpy sign into consideration

Answer 8

Oh so by low lattice energy we indirectly mean more energy is released when they break?

Answer 9

how can low lattice energy can give high hydration energy :)

Answer 10

So then why we say one is low and other high when we speak of solubility? Is it because of the sign difference?

Answer 11

yeah :/ according to the definition of lattice energy> ( The energy needed to break one mole of solid ionic lattice to form one mole of gaseous ions) = this is enthalpy lattice energy

Now when u talk about hydration enthalpy ( The energy releases when one mole of gaseous ions dissolve in water to produce an infitne solution) - this is enthalpy hydration

So when u hv high lattice energy say, the attractions between the position and negative ions are large, the u need high lattice energy to break it,

Similary in that case when u consider for hydration enthalpy, large amount of energy is released when this positive ions and negative ions make bonds with water molecules

Answer 12

Yeah I think I got it. Since both are high we see which is relatively more. That decides the solubility?

Answer 13

When we speak of solubility we dont say one is lower that the other, We normally talk about solubility down a group in the periodic table not for an individual substance. In that when u go down the group, the decrease in either lattice of hydration ("the decrease" ) as you go down with relative to each other is what determines its solubility down the gorup

Answer 14

and they both are related directly :) i mean the lattice energy and hydration energy :)

Answer 15

lattice or hydration*

Answer 16

Is my conclusion right? " Since both are high we see which is relatively more. That decides the solubility"

Answer 17

yeah kind of
I think you might want to read this http://www.chemguide.co.uk/inorganic/group2/problems.html

Answer 18

Reading it.

Answer 19

Wow this is quite something to learn about! I am sure I can get the hang of it after going through it a few more times. Thanks a lot both of you!! :)

Answer 20

I have one more doubt though: How does inert pair effect affect solubility?

Answer 21

how would you define inert pair effect?

Answer 22

reluctance of s electrons to take part in reaction?

Answer 23

i am not sure ? :/ @chmvijay

Answer 24

no idea i have to see now :) good question :)

Answer 25

exactly never came across something like that :/

Answer 26

Thanks :) I hope I get a good answer!