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Solution to Chemical Riddle #2

Tom Kuntzleman's picture
Wed, 05/07/2014 - 10:18 -- Tom Kuntzleman

Congratulations to Andres Tretiakov who solved Chemical Riddle #2.  In this particular riddle, we presented a twist on the famous “Disappearing Rainbow” demonstration.  You can purchase a pre-packaged version of this demonstration from Flinn Scientific. 

 

To conduct this demonstration, six beakers are arranged with different acid-base indicator mixtures as follows:

Beaker 1 contains an indicator mixture that is red in base and colorless in acid.

Beaker 2 contains an indicator mixture that is orange in base and colorless in acid.

Beaker 3 contains an indicator mixture that is yellow in base and colorless in acid.

Beaker 4 contains an indicator mixture that is green in base and colorless in acid.

Beaker 5 contains an indicator mixture that is blue in base and colorless in acid.

Beaker 6 contains an indicator mixture that is violet in base and colorless in acid.

Prior to the start of this experiment a very small amount of acid is poured into each beaker, rendering the contents of each beaker colorless.  To start the demonstration, a solution of base is poured into each beaker, which causes the color of each indicator mixture to be displayed.  After this, a sponge paint brush that has been soaked in acid is swirled into the contents of each beaker.  Of course the contents of each beaker turn colorless as a result.  Finally, a sponge paint brush that contains base is swirled into the contents of each beaker and the color returns!

Chemistry Topic: