Synthesis of Tin(II)Iodide
1. Purpose: To synthesize Tin (II) Iodide, a borderline ionic crystalline compound.
2. Theory: Tin (II) Iodide is not a thermodynamically favored substance. What this
means is that if you mix Tin and Iodine, nothing will happen. So we will have to
trick this substance into forming, using the mystical and vast chemical knowledge
of MSSR Godfrey and Welch. First, we will digest Tin in a concentrated solution
of HCl simmered over a hotplate:
Sn(s) + 2HCl(aq)  SnCl2(aq) + H2(g)
This solution will be fitered and stored. Next, you will react Zinc and Iodine in an
aqueous environment:
Zn(s) + I2(aq)  ZnI2(aq)
This reaction is extremely exothermic and caution must be used.
Finally we mix the two hot filtered solutions together:
SnCl2(aq) + ZnI2(aq)  SnI2(aq) + ZnCl2(aq)
The mixture is evaporated down some, then cooled to crystallize the SnI2, which
is not very soluble in cold water. The crystals are then suction filtered, rinsed, and
dried.
3. Procedure:
a. Day one: Mass out 5-7 grams of tin and place it in a 100ml beaker. Fill the beaker
to 40 ml with 6M HCl. CAUTION: this HCl is quite concentrated! Add one to
three drops of CuSO4 solution and place the beaker on a hot plate under the fume
hood to simmer for the rest of the day. Do the stoichiometric calculations to
determine the mass of Iodine you need to prep for the next day. Mass out the
iodine and place it in a CLEAN 250ml erlenmeyer flask and stopper it. Put you
name on it and store it until day 2. Your instructor will show you demos for
reacting the iodine and recrystalization.
b. Day two: Prepare a water bath in the plastic trays. Your instructor has already
shown you how to add 8g of zinc to the prepped iodine and add water to just
cover it. Swirl the flask, holding the bottom to check the temperature. Your
instructor will add powdered Zinc to start the reaction. Filter the SnCl2 solution,
rinse twice with a small amount of distilled water, and store it in a small stoppered
Erlenmeyer flask. When the iodine solution is fully reacted it will look grey, filter
and rinse as you did with the SnCl2 solution and store both solutions. Put you
initials on both and store them until day 3. Your instructor will show you demos
for using the Buchner funnel and pressing the filter cake dry.
c. Day three: Heat both solutions to just below boiling and pour the SnCl2 solution into
the ZnI2 solution. Evaporate the solution until its color becomes medium orange, then
start recrystallization. When your crystals are ready, suction Filter them in the Buchner
funnel and press them dry as demonstrated on day one. Mass the crystals wet, then put
them in the drying oven overnight and mass them dry.