Tetramethylammonium Triiodide
2 mL Erlenmeyer flask; put tetramethylammonium iodide (CH3)NI (0.50 g), and ethyl alcohol (20 mL). Add iodine (0.65 g). Heat in water bath and stir the mixture until all the white solid has dissolved. Allow to cool slowly to room temperature and finally cool on ice. Filter under suction and dry in air. Record the color of the product. Measure melting point. Record the weight obtained and calculate the percentage yield.
Analysis: One of the accepted ways for chemists to prove that they have made the compounds they claim is by obtaining satisfactory elemental analyses. This usually means determining the percentage by weight of one or more of the elements present in the compound. In the case of the compound you synthesized, iodine is the easiest element to determine by redox titration.
Dissolve sodium bisulfite NaHSO3 (1.04 g, 0.01 mol) in water (100 mL) to get 0.1 M NaHSO3. Fill buret with bisulfite solution. Accurately weigh 0.204 g of [unknown unit] mol?), dissolve in ethanol (10 mL), and titrate with bisulfite solution to get the exact concentration of 0.1 M NaHSO3.
Weight accurately about 0.20 g [unknown unit] mol?) of the product in a flask and dissolve in ethanol ([unknown unit] mL). Titrate iodine (from triiodide) with bisulfite solution until colorless. Write and balance the chemical equation. From titration data, calculate the molar amount of iodine in your sample of triiodide. Calculate the percentage purity of your tetramethylammonium triiodide product.
b) Tetramethylammonium Pentaiodide: Prepare the compound as described above, using 0.50 g of (CH3) [unknown unit] and 1 g of iodine. Observe the color of the dry product. Measure melting point. Calculate the percentage yield. Titrate iodine (from pentaiodide) with NaHSO3, as described above. Calculate the percentage purity of pentaiodide.