A sample of mercury with a mass of 114.0 g was combined

with 12.8 g of oxygen gas, and the resulting reaction gave
123.1 g of mercury(II) oxide. How much oxygen was left
over after the reaction was complete?

The answer I got was 3.7 grams. Am I correct?

1 answer

114.0g Hg = 0.568 moles
12.8g O2 = 0.400 moles = 0.8 moles of O
123.1g of HgO = 0.568 moles HgO
so, 0.232 moles of O = 3.712g

Looks good to me