On heating a sample of 25 mg hydrated compound (molecular weight $=250\,\mathrm{g/mol}$) in thermogravimetric analysis, 16 mg of dehydrated compound remains. The number of water molecules lost per molecule of hydrated compound is ____ .
(Molecular weight of water $=18\,\mathrm{g/mol}$)
Answer
Answer (as printed): 5
The options are missing from the source scan for this question, so there is nothing here for this letter to point at. The letter is what the book printed.
Explanation
Answer: 5 — 25 mg = 0.1 mmol of hydrate; 9 mg water lost = 0.5 mmol; 0.5/0.1 = 5 H₂O per formula unit.