[needhelp1212]

A solution of benzoic acid in 5% NaOH is placed in a flask. An equal volume of diethyl ether is then added and the mixture is stoppered, shaken and then allowed to stand and reach equilibrium. Ether is immiscible with aqueous solvents, and the mixture of liquids forms two layers: the ether layer and an aqueous layer.

(a) which liquid forms the top layer? briefly explain?

(b) which solvent contains the benzoic acid? briefly explain?

If hydrochloric acid is now carefully added to the mixture in order to neutralise the mixture, then the flask is stoppered, shaken and then allowed to stand to reach equilibrium again,

(c) now which solvent contains the benzoic acid? briefly explain?

Outline a procedure for separating a mixture of para-nitrphenol and naphthylene by exploiting their different solubilities.


Here is what I have:

a) diethyl ether is top and the squeous solution of benzoic acid and NaOH is the bottom based on densities.
b) the benzoic acid is contained within the aqueous solution because the acid reacts with the base
c) HCl would re-protonate the benzoic acid and thus an aqueous NaCl salt forms  with the Cl- ions and reforms and dissolves in the diethyl ether.

Here is where I am confused.  I know the benzoic acid is in the diethyl ether (well I am pretty sure) but I don't know why.  is it because diethyl ether dissolves almost everything?

and with outlining my own procedure I have:

para-nitrophenol and naphthylene form a homogeneous mixture and so initially separate, you add NaOH which would deprotonate the para-nitrophenol and would form the aqueous bottom layer which you would drain off to leave a pure naphthylene.  Then to separate the para-nitrophenol from the aqueous solution, you add HCl which would re-protonate the para-nitrophenol. 

Where I am stuck is that I don't know if an aqueous NaCl salt forms and I was also told my our instructor that ether would have to be added after the Hcl but I dont know why.

[kunjal8015]

density of diehtyl ether is 0.7134 g/cm3,
and desity of Benzoic acid is 1.32 g/cm3,

A) diethyl ether would at the top since it's less dense than benzoic acid.

B)the benzoic acid is contained within the aqueous solution because the acid reacts with the base
c)HCl would re-protonate the benzoic acid and thus an aqueous NaCl salt forms  with the Cl- ions and reforms and dissolves in the diethyl ether.

Here is where I am confused.  I know the benzoic acid is in the diethyl ether (well I am pretty sure) but I don't know why.  is it because diethyl ether dissolves almost everything?

if i am understanding you correctly, it is because when you add HCl back to the sol. you will NaCl and H2O as aqueous layer and you will have diethyl ether and in one those layer you will have benzoic acid. now becasue the solution is neither basic or acidic it will not react so only place benzoic acid can go is in diethyl ether because they both have huge non polar parts, if you look at the structure. like dissolves like so you will have benzoic acid in diethyl ether and another layer of aqeous NaCl.

I hope that clears it up. if you question let me know.