19. Iodine, I2, reacts with the thiosulfate ion to give the iodide ion and the tetrathionate ion, S4O62-. 

19.1 Balance the chemical equation for the above reaction. 

19.2 If 10,0 grams of iodine is dissolved in an appropriate manner to give 300 cm3 of solution, what is the molarity of the iodine solution? 

19.3 What volume of a 0,125 M sodium thiosulfate solution will be needed for complete reaction of the solution in (19.2)?