Need Help Asap...solubility!

[ROSS99]

Why does the solubility of a solid increase as the temperature of the solution increases? what happens at the molecular level?

 

What property of the solution is illustrated the moment crystals start forming?

 

i have an answer for each but i am not positive...any help would be greatly appreciated.

 

thank you

[blike]

Let's see what you got for your answers.

[ROSS99]

The relationship between the solubility of potassium nitrate and the temperature of its solution is that as the temperature increases the solubility of potassium nitrate also increases. The solubility of potassium nitrate increases as the temperature increases because it is a solid and for most solids an increase in temperature results in greater solubility. This pattern occurs because increased temperature means increased molecular motion, which breaks apart the firm bonds holding the molecules in a solid together. When a solid comes in contact with a liquid solvent some of the molecules in a solid will break free and mix into the liquid. As more solute is added into the solvent, some of the molecules that broke free will return as they bump into the solid. When the solid has reached its maximum solubility the ratio between the number of molecules breaking free from the solid and attaching themselves to the solid is exactly the same. By increasing the temperature the molecules begin to move faster making it more likely for molecules on the surface of the solid to break free and less likely for molecules in the solution to become attached to the solid. Therefore, the addition of heat facilitates the dissolving reaction by providing energy to break the bonds in a solid and allowing the molecules to become detached.

 

The moment crystals begin to form, the saturation point of the solution is illustrated. When less solvent is present, the concentration of the solute quickly exceeds the solubility causing the excess solute to crystallize out.

 

??

[Klaynos]

I think you've got the answers your expected to, unless you know quantum statistical mechanics?

[ROSS99]

to idea what that is

[Klaynos]

to idea what that is

 

WEll good, you're answers are probably right then

[ROSS99]

thanks..if anyone has some more suggestions that be great

i also have one more question:

 

 

Other than temperature, identify two other factors that can increase the solubility of a solid.

[Ducky Havok]

I might be wrong, but I believe pressure and surface area also effect solubility of a solid.

[ROSS99]

molecule size and also the molecule’s charge. Compounds of ions with small charges tend to be more soluble and compounds of ions with small charges also tend to be more soluble.

 

MAKE SENSE?

[Inspiration]

solid (melts) liquid (evapourates) gas

 

when you are making coffee or tea, why do you make it in hot water??? it dissolves faster, because the mollecules of water are moving faster and hence hitting it at a faster rate.... try applying this reasoning to your question.

[Inspiration]

thats already been said though.. also,

 

look up salts, they dissolve quite readilt in most instances (not just NaCl, but nitrates ect. as well).

 

Alkalie metals vs alkalie earth metals. i believe you will find there is a subtle difference ie, the alkalies are generally soluable whereas the alkalie earths are not...

 

Other than that, E^0 values (E naught) and KSP (slubility constants) will come in handy for you at some stage in senior highschool too but dont worry about those too much for now. Fun times await you, our chemistry teacher is that fine line between genious and crazy, also he believes everyone is a mindreader and as genious as he is...