Chemistry

Practical CI  13
Calculation of the yield. (Based on Iodine)

Product yield
Weight of Iodine taken for the synthesis 2.0 grams  2.0126.92  0.01576 gm atom
Boat Weight 0.9314gWeight of Boat  product 3.0462 gProduct yield of Tin Iodide obtained is 3.0462g - 0.9314g  2.1148g
Iodine content of Tin Iodide
Assumption Second titer value is the accurate one.
Weight of SnI4 sample taken for analysis 0.25 gm
The sample is titrated with 0.025 molLit KIO3 solution. Titer value is 32 ml.
The reaction is IO3-  2I-  6H  3Cl-    3ICl  3H2O
IO3- is equivalent to 2 I
Atomic Weight of Iodine 126.92 Atomic Weight of Tin 118.70.

Molecular weight of Tin Iodide, SnI4  118.70  (126.92x 4)  626.38 gm

1000 ml of 1 mol IO3- solution  2 gm atoms of Iodine  2x 126.92  253.84 gm I2
32 ml of 0.025 mol of IO3-  (253.841000) x 0.025x 32.0  0.20307 gm I2
0.20307 gm I2 is present in 0.25 gram of the sample taken
Iodine content of the yield  (0.203070.25) x 2.1148  1.71781 gm
Iodine content in the product, SnI4  (1.71781 gm 2.1148 gm) x 100  81.228
The theoretical Iodine content of pure SnI4  (4x 126.92) 626.38  81.05
The experimental value is slightly more than the theoretical value. This may be due to the  ve
error induced by the fleeting end point.
The  yield obtained
Assuming the purity of Iodine as well as the product as 100, the  yield obtained is,
 Iodine content of SnI4 yield x 100      1.71781 gm x 100  85.89
Iodine taken                 2.0 gm

The balance Iodine would have been lost during the refluxing process, since Iodine is volatalisable.
Complementary work.

1 a. When water was added to the acetone solution of SnI4, the solution turned pale yellow.  The reason for this is SnI4, being an unstable compound, undergoes slight decomposition in aqueous solution. But the solubility of Iodine in water is very low say of the order of 0.04 parts  100 parts at 30 OC when equilibrium is reached, the colour of solution is pale yellow.

1 b. When saturated solution of KI was added to the acetone solution of SnI4, the solution turned dark purple.  The reason for this is SnI4, being an unstable compound, undergoes slight decomposition in aqueous solution. But the solubility of Iodine in KI solution is very high, the Iodine produced by decomposition dissolves in the KI solution and further amount of SnI4 decomposes to attain equilibrium, and so the colour is the characteristic purple colour of the Iodine in organic medium, say, acetone.

2. PbI4 can not be made in this manner. Akhmetov (1973, P. 405) states, the stability of binary compounds of Ge (IV), Sn (IV), Pb (IV)  decreases in the series.  Iodides  are known only for Ge (IV) and Sn (IV).