Reversable Reaction

Chemicals and Solutions: 

KOH solution (8 g/ 300 ml water)

10 g dextrose (glucose)

Methylene blue indicator

Materials: 

500 ml florence flask with rubber stopper

Procedure: 

Put the potassium hydroxide solution in the florence flask and then add the 10 g of dextrose. Stir to dissolve the dextrose and then add six drops of methylene blue. When the indicator is initially added to the dextose/KOH solution, the solution appears blue. The color gradually fades to produce a colorless solution. To restore the color, give the flask one or two vigorous shakes. The color will reappear and then slowly fade.

 

Discussion: 

The reaction:   Initially  alkaline dextrose reduces methylene blue to form a colorless solution.   

 

Upon shaking, oxygen from the air dissolves in the solution.  This oxygen then reoxidizes the dye back to the blue form.

 

                                   

 

To schedule a demonstration, please send an email to the demonstration lab.

 

Contact:

Eric Camp

Lecture Demonstration Technician

Bagley Hall 171

(206) 543-1606

ericcamp@uw.edu

 

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