In: Chemistry
There are many other types of clock reactions. One that is sometime used for educational purposes similar to this lab is the "Old Nassau Reaction". Provide a list of the chemical reagents used in the Old Nassau reaction and a list of chemical reagents used in the Vitamin C clock reaction. Which one of these reactions would you regard as greener and why?
The reactions involved in Old Nassau Reaction are as follows.
1. Na2S2O5 + H2O 2 NaHSO3
2. IO3- + 3
HSO3-
I- + 3 SO42- + 3
H+
This reaction reduces iodate ions to iodide ions.
3. Hg2+ + 2 I-
HgI2
Orange mercury iodide solid is precipitated until the mercury is
used up.
4. IO3- + 5 I- + 6 H+ 3 I2 + 3 H2O
The excess I- and IO3- undergo the iodide-iodate reaction
5. I2 + starch a blue/black complex
A blue/black starch-iodine complex is formed.
The reactions involved in Vitamin C clock reaction are as follows.
1. 2I- + H2O2 I2 + H2O
2. I2 + Vitamin C I (colorless)
Here, Vitamin C clock reaction is regarded as greener.
Explanation: There are are no harmful by-products in Vitamin C clock reaction, whereas there are harmful sulfate by-products in Old Nassau Reaction.