1 g of Mg is burnt in a closed vessel which contains 0.5 g of $O_{2}$. Which reactant is left in exc

Question

1 g of Mg is burnt in a closed vessel which contains 0.5 g of $O_{2}$. Which reactant is left in excess and what is the weight of the excess reactant in g?

Professor PC Thomas Classes · Answer

2Mg + $O_{2} \rightarrow$ 2MgO. 0.5g $O_2$ needs 0.75g Mg. Mg left = $1 - 0.75 = 0.25g$.