Question

1 gram of magnesium is burnt with 0.56 gram of O2 in a closed vessel. Which reactant is left in excess and how much

Answer 1

2Mg +O2 -----> 2MgO

Here 48 g of Mg reacts with 32 g of O2

Hence, 1 g of Mg will react with 32/48 = 0.67 g of O2

But Given Amount of O2 = 0.56 g which is less than required.

Hence, O2 is limiting reagent.

Hence Mg is Left in excess

32 g of O2 reacts with 48 g of Mg.

Hence 0.56 g will react with = 48*0.56/32 = 0.84 g of Mg

Hence, Amount of Mg left = 1-0.84 = 0.16 g

Answer 2

2MgO+O2=2MgO

Given =1gm of MgO and 0.56gm of O2.

Now see the equation,

2*24 gm of MgO requires 32gm of o2,

So, 1gm of MgO require oxygen =32/24*2=0.667

As o2 available is0.56 which is less than the required amount of oxygen

Hence oxygen is the limiting reagent.