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Q-11
As a point of information, it is not possible to separate I2 and I3
-
in aqueous solution. Fortunately the half-
cell potentials for the reduction of I2 to I
-
, and of I3
-
to I
-
are nearly the same. You may assume that your
measurement is for the I2/I
-
half-cell.
Connect the I2/I
-
half-cell to the Cu/Cu
2+
half-cell previously prepared and measure the electrode potential.
Similarly, connect it to the Ag/Ag
+
half-cell and measure the electrode potential. (Caution: the iodine
solution slowly stains the polystyrene cup.
After making your voltage measurements,
immediately remove the iodine solution with a Pasteur pipet, and rinse the well with a bit of
water.) These results will be used to place the I2,/I
-
half-cell in the proper position with respect to the
metals.
Discard all of these solutions in the “Toxic Metal Ion Waste” container in the fumehood
Part II. Halogen Displacement Series
A. Determination of the Characteristic Colors of the Halogens in CH2Cl2
1.
Determine the colors of aqueous solutions of various halides. Refer to the bottles of stock solutions
in the fume hood. What is the color of:
a)
KCl in water?
b)
KBr in water?
c)
KI in water?
Record your observations.
2.
Remember that water and CH2Cl2 are immiscible. Is the water layer above or below the CH2Cl2
layer?
Caution
- chlorine water may cause serious burns. ** DO NOT INHALE VAPORS**. Shake
2 mL of chlorine water with 2 mL of CH2Cl2 in a small test tube using a green rubber stopper.
Note the color of the CH2Cl2 layer and record your observations.
3.
Caution - bromine water may cause very serious burns. ** DO NOT INHALE VAPORS**.
Shake 1 mL of bromine water with 2 mL of CH2Cl2 in a small test tube using a green rubber
stopper. Note the color of the CH2Cl2 layer and record your observations.
