1.0 g of magnesium is burnt with 0.56 g O₂ in a closed vessel.Which reactant is left in excess and how much? (At.wt.Mg=24, O=16)

Options

(a) Mg,0.16g
(b) O₂,0.16g
(c) Mg,0.44g
(d) O₂,0.28g

Correct Answer:

Mg,0.16g

Explanation:

Initially Mg +1/2 O₂→MgO (or)
1/24 mole 0.56/32 mole
0.0416 mole 0.0175 mole
(0.0416-2 ×0.0175) (2 ×0.0175) mole
=0.0066 mole
mass of Mg=0.0066 ×24
=0.158 ≈ 0.16g