Question

 

1. shake sorting funnel with 1-butanol 20mL and 0.5N acetic acid aqueous solution 20mL in it.

2. When water layer and butanol layer are separated, extract 0.5N acetic acid 10mL
to beaker A and add distilled water 10mL

3. Titrate solution in beaker A with 0.5N NaOH aqueous solution.

4. Extract 1-butanol to beaker B and tiltrate with 0.5N NaOH

5. Calculate Distribution coefficient

What would be ideal Distribution Coefficient K?

Answer 1

Distribution coefficient or partition coefficient (kd) is the ratio of the concentration of a solute in the organic layer to that in the aqueous layer,the two solvents being in equilibrium with each other.

kd=[Solute]organic/[S] aqueous

[Solute]organic=concentration of a solute in the organic layer

[S] aqueous=concentration of a solute in the aqueous layer

Your solute is acetic acid which gets distributed between 1-butanol (organic layer) and aqueous layer. On shaking the separating funnel,a part of the acetic acid goes into the organic layer and another part goes to the aqueous layer. As you titrate Beaker A, the part of acetic acid in the aqueous layer is titrated by NaOH.Thus ,the concentration of acetic acid in aqueous layer ([Solute]aqueous)is determined by calculations.

Using equation,

N(NaOH) *V(NaOH)=N(acetic acid)*V(acetic acid)

N(NaOH)=normality of NaOH=0.5N

N(acetic acid)=?

V(NaOH)=volume of NaOH used up

V(acetic acid)=20 ml (10+10)

Titrate beaker B to titrate acetic acid dissolved in 1-Butanol.Calculate the concentration of acetic acid present in organic layer ([Solute]organic).

Thus calculate kd.