T HE O XIDATION S TATES OF T IN
CHEM 230 LABORATORY
(Include the following at beginning of Report)
Part A: Mass Tin: ____________ Mass Iodine: ____________
Part B: Mass Tin: _____________ Mass Zinc: ____________ Mass Iodine: ________
Mass of Sn(IV) product: __________________
Mass of Sn(II) product: ___________________
1.
2.
In Part A of this experiment, we have told you that the product you were forming
is SnI4. But do you have any experimental proof that this is the product that you
made?
a)
Determine how many moles of I2 were used in the reaction and how
many moles of Sn were used in the reaction. (Show your work)
b)
What is the ratio of moles of Iodide to Sn? Does this support the
claim that this product is SnI4?
The typical oxidation state shown by elements in Group 14 is +4, found in
compounds like CCl4, SiCl4 and SnO2. In the last 2 labs, we have looked at Pb
and Sn.
a) What is the condensed electron configuration of Pb and Sn?
(for example [He] 2s2 2p6)
In order to have the outer 4 electrons involved in bonding (as in SnI4), it is
necessary to promote an s electron to an empty p orbital, and following
hybridization these 4 unpaired electrons can form covalent bonds.
b) In order to promote an s electron to an empty p orbital, energy is
required. Is it energetically favourable to promote this electron when
bonding? Why or Why not?
Alright, the typical oxidation state of this group may be +4, but as you go down
the periodic table, the +2 oxidation state becomes prevalent, this is often
explained by the "inert pair effect". By the time you get to Sn, the +2 state is
quite common but Sn still prefers the +4 state. Pb is different, it actually prefers
the +2 to the +4 state.
c) Look in your text book (try the index) or another source, and briefly
explain what the “inert pair effect” is AND what it has to do with the
oxidation states of Sn and Pb. (Note: The concept is complex and not fully
understood, just show that you have some idea of the concept. If you don’t
own the text, other texts in the library will have information.)
3.
In the formation of the tin (II) iodide, we used the following reactions.
The tin is made to react with hydrochloric acid forming a solution of stannous
chloride.
Sn + 2HCl
6 SnCl
2
+ H2
The iodine is made to react with zinc in a water medium forming a solution of
zinc iodide.
I2 + Zn
6 ZnI
2
The two solutions are then mixed and stannous iodide, precipitates from the
solution according to the reaction:
ZnI2 (aq) + SnCl2 (aq)
6 SnI (s) + ZnCl
2
2
(aq)
leaving the very soluble zinc chloride in solution.
a) Calculate the % yield of your SnI2.
b) In part B, the iodine is made to react with zinc. Write the chemical halfreactions (including the half-reactions voltage potentials) and then write the
overall reaction and the overall voltage potential. Is this a spontaneous reaction?
4.
Why do you think a reflux apparatus was used in this experiment instead of
simply boiling the solution in a beaker?
5.
In Part C, the reaction of SnI4 is dissolved in acetone and then reacts with
water to form tin hydoxide. This tin hydroxide is classified as amphoteric.
What does that mean? AND did your experimental results confirm that this
was indeed amphoteric? (explain from your results)