The number of grams of hydrated that student must weigh out in order to get desired amount of the anhydrous compound is 81.68 grams
find the molar mass of Bai2 and molar mass of barium iodide dihydrate
that is Bai2 = 137.3 +(2x127)=391.3 g/mol
Bai2. 2H2O = 137.3+(2 x127) +2 (2+16)=427.3g/mol
using ratios and letting the mass of hydrate be represented by Y
427.3/391.3=Y/74.8
multiply both side by 74.8
Y=81.68 grams