Answer:
30.8 grams O
Explanation:
In H₂O, there are 2 moles of hydrogen for every 1 moles of oxygen. You can use this to convert between moles of H and moles of O. Then, you can use the molecular weight of oxygen (15.998 g/mol) to convert between moles O and grams. The answer should have 3 sig figs because the given value (3.85) also has 3 sig figs.
3.85 moles H 1 mole O 15.998 g
-------------------- x ------------------ x -------------------- = 30.8 grams O
2 moles H 1 mole O
