# Homework Help: Electrical conductivity of solutions and titration curve question

1. Aug 24, 2008

### Paulo2014

hi
The following question I am stuck on:

Some automatic titrators used in modern analytical laboratories measure the electrical conductivity of the solution in the flask as the titration proceeds. The equivalence point is determined by monitoring changes in the conductivity of the solution. These changes depend on the concentration and the relative conductivities of the ions in solution.

The relative conductivities of some ionic species are shown in the table below.

Ionic species
Relative conductivity
Na+, Cl–, CH3COO– 1

OH– 3

H3O+ 5

(a) Sketch the plot of conductivity of the titration mixture against the volume of NaOH added for the titration of 1.00 mol L–1 HCl with 1.00 mol L–1 NaOH. (See hint below.)

Justify your answer by showing how significant points on the graph were determined OR by discussing the reasons for the changing conductivity.

(b) Show on the graph drawn in (a) how the shape will change if 1.00 mol L–1 CH3COOH is used in the titration instead of HCl. Justify your answer.

Hint: It may be useful to construct a table to identify the ions present and their relative concentrations and conductivities at different stages in the titration, including a point after the equivalence point. It can be assumed that the total conductivity in a solution is the sum of conductivities of the ions present.

How would I do this?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution