[hydrowire]

I have a compound and it says it is hydrated, waht does hydrated means anyway?

e.g. hydrated ethanedioic acid, H₂C₂O₄.2H₂O

does this solution forms ions? how does the water molecule relates to the ethanedioic molecule?

[Borek]

Solid forms crystals. In crystal lattice there are molecules of water per every molecule of substance. That's what hydrated means in case of oxalic acid.

Once the substance is dissolved every ion is surrounded by water molecules, but not in stoichiometric ratio. This is called hydration too (unless my English fails here).

Try wikipedia on hydrates.

[hydrowire]

Why we need hydrated oxalic acids? whats the difference between non hydrated(is it called anhydrous?) oxalic acids and hydrated oxalic acids?

[Dude]

Hydrated in this case means that a somewhat stable amount of water is adsorbed by the salt.  If you were to make a 1 M solution of oxalic acid, the 2 moles of water are INCLUDED as part of the molar mass.  Thus, you would need more of a hydrated oxalic acid salt to attain a 1 M solution than an anhydrous oxalic acid salt since a portion of the molar mass is water.

[hydrowire]

So what does this sentence means: To determine the mass of sodium ethanedioate(oxalate) used to prepare a solution containing sodium ethanedioate(oxalate) and hydrated ethanedioic(oxalic) acid.

how can it forms hydrated oxalic acid? by adding water with the right amount?

Is it correct that,
Sodium Oxalate - aqueous solution?
hydrated oxalic acid - solid crystal?


thx in advance.

[Borek]

Why we need hydrated oxalic acids? whats the difference between non hydrated(is it called anhydrous?) oxalic acids and hydrated oxalic acids?

Difference lies in molar mass, as Dude already wrote.

Why do we need them is wrong question. Some substances just don't want to crystallize as non hydrated. Some substances can't be dehydrated without destroying them. Thus in many cases that's not a case of "why do we need them", it is a case of "we have no other choice".

[Borek]

So what does this sentence means: To determine the mass of sodium ethanedioate(oxalate) used to prepare a solution containing sodium ethanedioate(oxalate) and hydrated ethanedioic(oxalic) acid.

I don't get it. Please post complete question.

[hydrowire]

Opps, sorry. The sentence is actually a purpose for an experiment.

Purpose: To determine the mass of sodium ethanedioate(oxalate) used to prepare a solution containing sodium ethanedioate(oxalate) and hydrated ethanedioic(oxalic) acid.

[Borek]

Perhaps there will be something more in the experiment description, but in this particular case "hydrated" can be omitted as well, not changing the meaning.

Oxalic acid crystallizes as a hydrate, thus it is used in this form to prepare any solutions. Period.

I am known to be ocassionally wrong, especially when there are some language subtleties at work, so second opinion will not do any harm.

Anybody?

[hydrowire]

From my understanding, I can see that it is using sodium oxalate to prepare sodium oxalate itself and hydrated oxalic acid.

Have 4 Materials in this experiment though.
KA1: a solution containing hydrated ethanedioic(oxalic) acid, H₂C₂O₄.2H₂O, and sodium ethanedioate(oxalate).
KA2: KMnO₄
KA3: OH- ions(NaOH)
KA4: H₂SO₄
and lastly phenolphthalein as indicator.
This volumetric analysis experiment consist of acid base and redox titration.

Procedure:
i)KA1 was titrate with KA3 with phenolphthalein as indicator.
ii)Then KA1 again is titrate with KA2 with sulfuric acid added in.

There are few things I'm not sure about this experiment, hope someone might help out.

How it is posible to prepare a solution containing sodium oxalate and hydrated oxalic acid with sodium oxalate itself?
Is sodium oxalate - solid?
hydrated oxalic acid - solid?
after adding water will become KA1?

Procedure (i) will be:
H₂C₂O₄ + 2NaOH -> Na₂C₂O₄ + 2H₂O
and Procedure (ii) will be:
5C₂O₂^2- + 2MnO₄^- + 16H⁺ -> 10CO₂ + 2Mn²⁺ + 8H₂O
Am I right with my chemical equations?

really appreciate any help.

[Borek]

KA1: a solution containing hydrated ethanedioic(oxalic) acid, H₂C₂O₄.2H₂O, and sodium ethanedioate(oxalate).

As I supposed - hydrated doesn't mean anything here, as long as we are talking about number of moles. But you are asked to calculate mass of hydrated oxalic acid used to prepare the solution - thus you have to take mass of water into consideration as well.

How it is posible to prepare a solution containing sodium oxalate and hydrated oxalic acid with sodium oxalate itself?

Who told you it is possible?

Is sodium oxalate - solid?

yes

hydrated oxalic acid - solid?

yes

after adding water will become KA1?

KA1 can be prepared in several ways. You can weight some sodium oxalate, some oxalic acid (hydrated!) and dissolve them. But you can as well take oxalic acid solution (prepared with hydrated acid) and add some sodium hydroxide, or you can take sodium oxalate solution and add some hydrochloric acid - in the last case you will have solution containing oxalic acid, oxalate and some NaCl which is an inert salt in case of both titrations.

Am I right with my chemical equations?

Almost. C₂O₄^2- instead of C₂O₂^2- but it was probably a typo on your side.

Don't worry about hydrated part - it is important only when calculating mass of the solid. Solutions prepared with hydrated substance or anhydrous substance are in most cases identical.