Question

What is the purpose and idea behind the experiment of conducting conductometricic titration of H2(SO4) and Ba(OH)2? what sources of error can be made and how these errors would affect the result?

Answer 1

PURPOSE OF THE EXPERIMENT :

To titrate a barium hydroxide solution of unknown concentration with a sulfuric acid solution of known concentration and to determine the concentration of the barium hydroxide solution

IDEA BEHIND THE EXPERIMENT :

The conductivity of a solution is dependent on several factors, including the concentration of the solute, the degree of dissociation of the solute, the valence of the ion(s) present in the solution, the temperature, and the mobility of the ions in the solution.

In this case, we will be titrating a solution of barium hydroxide, Ba(OH)2, with sulfuric acid, H2SO4. Initially the Ba(OH)2 will be almost completely dissociated into Ba2+ and OH- .

With the addition of the H2SO4 the following reaction takes place:

Ba2+ (aq) + 2 OH- (aq) + 2 H+ (aq) + SO42- (aq) = BaSO4 (s) + H2O (l)

The barium sulfate, BaSO4, is fairly insoluble and precipitates out of solution. The hydronium and hydroxide ions combine to form water. Neither of the reactant products contribute very much to the conductivity of the solution, thus as the titration takes place the conductivity will decrease. At the equivalence point, when enough H2SO4 has been added to react with the available Ba(OH)2, the conductance of the analyte is at it’s lowest point. Adding more titrant will cause the conductance of the analyte to increase again. Thus a plot of conductance vs. volume of H2SO4 added will result in a “V” shaped graph. We will take the curve fit for the line on either side of the equivalence point and solve for the intercept of the two lines to derive an exact value of H2SO4 used..

POSSIBLE ERROR:

The level of the water should be sufficient to cover the flow-through holes on the sides of the Conductivity electrode. Otherwise the reaction will not occur.

If the water level is below the holes of the Conductivity electrode, more distilled water is added until the holes are submerged.

The holes on the side of the electrode should be checked to find out if there are any air bubbles trapped in the tip of the electrode. If there are air bubbles trapped in the tip, the electrode should be shaken or tapped to dislodge the air bubbles.The presence of air bubbles will also prevent the reaction from occuring because the reaction takes place at the surface of the electrode