Answer: 193 grams
Step-by-step explanation:
The gram-formula mass of elemental hydrogen is about 2 g/mol, meaning that if you consume 6.5 grams of elemental hydrogen, you will consume 6.5/2 = 3.25 moles.
This means that since for every 2 moles of hydrogen consumed, 1 mole of tin is produced, we need to find the mass of 3.25/2 = 1.625 moles of tin.
Since tin has an atomic mass of 118.71 g/mol, the theoretical yield of Sn is (118.71)(1.625) = 193 grams.