The Student Room Group
Uni students - Complete our survey >>
Uni students - Complete our survey >>
Uni students - Complete our survey >>

Questions about chemical reactions.

Hello!

I would like someone explain to me why and how NaCl in presence of aqueous solution becomes Na+, Cl-. What leads to this, because NaCl already is stable, and i don't understand how H2O does this with NaCl.

The same explanation could be applicated to an acid - base like HCl + NaOH ?

Thank you!
Water weakens the ionic interactions between the ions in an ionic substance.

So an ionic substance can be loosely seen as its separate ions when in aqueous form.
NaCl is stable on it's own, but it's 'more stable' in water. When dissolved, each ion will be surrounded by multiple water atoms weakly bonded to it, which is more favourable in terms of energy.

You can also think about it in terms of entropy - a solution is much more disordered than a solid crystal; there are many more ways of arranging a solution than a crystal.

You can also think about the surface of the crystal - the outer ions will not be completely surrounded by counter ions, so will be vulnerable to water.

I'm not sure what you mean by the same explanation applied to acid-base reactions.
(edited 9 years ago)
Reply 3
Avatar for Borek
Borek
4
NaCl, being an ionic solid, already contains Na+ and Cl-. During dissolution they are just separated. Note that every dissolution means separation of the molecules/ions from the solid, NaCl is not different.
Original post by Borek
NaCl, being an ionic solid, already contains Na+ and Cl-. During dissolution they are just separated. Note that every dissolution means separation of the molecules/ions from the solid, NaCl is not different.


Yes, i know that.
What i don't understand is how H2O breaks this molecule. I believe is because her polarity, and the polarity of NaCl. But i don't know if i'm right and if yes, how this is done. And the most intrigant thing for me is that NaCl is already stable! I would like to understand why Na breaks her bond with Cl.
Original post by laura.g.berger
Yes, i know that.
What i don't understand is how H2O breaks this molecule. I believe is because her polarity, and the polarity of NaCl. But i don't know if i'm right and if yes, how this is done. And the most intrigant thing for me is that NaCl is already stable! I would like to understand why Na breaks her bond with Cl.


NaCl is NOT a molecule.

The strength of the bonds formed between water and the separate Na+ and Cl- ions plus the increased entropy of the solution is greater than the electrostatic forces within the giant lattice ...
When NaCl is added to water, so it comes to a dissociation, that is to say the solid bond NaCl is split in two ions, namely Na+ and Cl-.
Original post by laura.g.berger
Hello!

I would like someone explain to me why and how NaCl in presence of aqueous solution becomes Na+, Cl-. What leads to this, because NaCl already is stable, and i don't understand how H2O does this with NaCl.

The same explanation could be applicated to an acid - base like HCl + NaOH ?

Thank you!


water is a polar molecule, the oxygen is more electronegative than the hydrogen atoms. This means that the oxygen is slightly negative and the hydrogen is slightly positive. You know that the Na is positive and that the Cl is negative, so the positive hydrogen is attracted to the negative Cl and the negative oxygen is attracted to the positive Na pulling the lattice apart. :smile:
Original post by ThatMadClown
water is a polar molecule, the oxygen is more electronegative than the hydrogen atoms. This means that the oxygen is slightly negative and the hydrogen is slightly positive. You know that the Na is positive and that the Cl is negative, so the positive hydrogen is attracted to the negative Cl and the negative oxygen is attracted to the positive Na pulling the lattice apart. :smile:


Oh! Now, this make sense for me. I mean, if is correct, thank you for your answer, and all your answers, guys!
I remember i read something like you said in somewhere long ago but i did not remember exactly what i read, so that's why i asked here, to make sure.
Original post by laura.g.berger
Oh! Now, this make sense for me. I mean, if is correct, thank you for your answer, and all your answers, guys!
I remember i read something like you said in somewhere long ago but i did not remember exactly what i read, so that's why i asked here, to make sure.


No problemo :smile: is this for GCSE or A-level?
I think its because the attraction of na+ and cl- to water is stronger than the attraction to each other?????

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you