Question

1.0 g of magnesium is burnt with 0.56 g 0, in a
closed vessel. Which reactant is left in excess and
how much ?
(At. wt. Mg = 24 ; O = 16)
1) Mg, 0.16 g
(2) 02, 0.16 g
3) Mg, 0.44 g
(4) O2, 0.28 ga.​

Answer 1

Answer:

1).Mg, 0.16g

Explanation:

The equation is as follows:

2Mg + O2  ------>  2MgO

(s)      (g)                (s)

Therefore 2 moles of Mg require 1 mole of O2 to produce 2 moles of MgO.

Calculate actual moles.

moles= mass/ molar mass

Mg=    1/24  = 0.041667

O2=   0.56/32 = 0.0175

MgO=

Mole ratio of Mg: O2   = 2:1

find mass of Mg that reacts:

that means 2 mole of Mg reacts with 1 moles of O2

If 1 = 2 

Then 0.0175 = 0.0175 x 2

                     =0.035 moles of magnesium

mass of magnesium that reacts:

mass= moles x molar mass

        = 24 x 0.035

         

              0.84 g

That means that of the 1 gram of magnesium that reacts only 0.84 grams is used

Therefore magnesium is in excess and by 0.16

Answer 2

Explanation:

1 . will be answer mg will be in excess and by 0.16 g as