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Sulfuric acid as a dehydrating agent

Description

These two demonstrations illustrate the phenomenon of dehydration as distinct from drying. Concentrated sulfuric acid removes water of crystallisation from hydrated copper(II) sulfate and ‘the elements of water’ from sucrose. An extension of the discussion to the oxidising action of concentrated sulfuric acid is possible.

Type of Activity

:
demonstration

Audience

:
Teacher

Age Group

:
11 to 18 years

Credits

:
This is an experiment from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry.
sulfuric-acid-as-a-dehydr...

 


 


Apparatus Chemicals

For one demonstration of each reaction the teacher will need:

Eye protection

Access to a fume cupboard with good all-round visibility

Beaker (100 cm3)

Large watch glass or white tile

Measuring cylinder (25 cm3)

Measuring cylinder (10 cm3 or 5 cm3)

Sucrose (table sugar), 50 g

Concentrated sulfuric acid (CORROSIVE), approximately 20 cm3

Hydrated copper(II) sulfate (HARMFUL, DANGEROUS FOR THE ENVIRONMENT), 3 g

Cobalt chloride paper (optional) (TOXIC)

Potassium dichromate(VI) paper (optional) (VERY TOXIC)

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

 


 


 



 


These two demonstrations illustrate the phenomenon of dehydration as distinct from drying. Concentrated sulfuric acid removes water of crystallisation from hydrated copper(II) sulfate and ‘the elements of water’ from sucrose. An extension of the discussion to the oxidising action of concentrated sulfuric acid is possible.

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 .