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A conductimetric titration using acids and alkalis

Description

This titration allows you to observe how acid neutralisation by an alkali is linked to the changes in ionic concentrations resulting from reaction between hydrogen ions and hydroxide ions.

Credits

:
This is an experiment from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry.
a-conductimetric-titratio...



Apparatus Chemicals

Eye protection for the teacher and for any members of class who assist at the bench

Test-tube (150 x 25 mm)

Test-tube rack

Beakers (100 cm3), 2

Measuring cylinder (100 cm3)

Glass rod

Burette (50 cm3)

Clamps (2) and stand

Small funnel (for filling the burette)

White tile (for standing beaker on during titration) and white card background (for class visibility)

Pair of carbon electrodes (Note 1) in holder, with 4 mm plug adapters

Plug leads (4 mm plug at each end), 4

Bulb (12 V) in holder

AC demonstration ammeter

Low voltage AC supply (Note 2)

Each demonstration requires:

Barium hydroxide solution, 0.10 M, (HARMFUL, IRRITANT), about 200 cm3

Dilute sulfuric acid, 1.0 M, (IRRITANT), about 25 cm3

Purified (distilled or deionised) water

Phenolphthalein indicator solution (HIGHLY FLAMMABLE)

Refer to Health & Safety and Technical notes section below for additional information.

 


Solid barium hydroxide (CORROSIVE) contains water of crystallisation, and reacts with carbon dioxide from the air while in storage.  It is only slightly soluble in water (maximum 4 g in 100 cm3) but the solution is much more alkaline than limewater. Make 250 cm3 of the solution. Purified water should be boiled to remove carbon dioxide before being added to solid barium hydroxide. Once prepared the solution is very sensitive to carbon dioxide and immediately goes cloudy (barium carbonate) when exposed to the atmosphere. All fresh solutions, which will be alkaline and may irritate sensitive skin, must be protected with a soda lime guard tube. For all these reasons, it is important to check the concentration of the solution before the demonstration to ensure it is reasonably close to 0.10 M – an exact concentration is not necessary. To do this titrate 50 cm3 of the solution with the dilute sulfuric acid (1.0 M), to be used in the experiment, using phenolphthalein indicator (two drops). A titre value between 4 cm3 and 6 cm3 is acceptable.





student worksheets 




Page last updated October 2015

Acid neutralisation by an alkali is linked to the changes in ionic concentrations resulting from reaction between hydrogen ions and hydroxide ions.

ADDITIONAL INFORMATION

This is a resource from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry. This collection of over 200 practical activities demonstrates a wide range of chemical concepts and processes. Each activity contains comprehensive information for teachers and technicians, including full technical notes and step-by-step procedures. Practical Chemistry activities accompany Practical Physics and Practical Biology.