Question

The chemical equation below shows the burning of magnesium (Mg) with oxygen (O2) to form magnesium oxide (MgO).

Answer 1

For every 2 mole Mg we need 1 mole O2 ( based on the equation). since there is 4 mole Mg we need 2 mole O2. one mole O2 is 32 gram so 2 mole would be 64 grams.

Answer 2

Answer: 64 grams of $O_2$ will be required to react completely with 4 moles of Mg.

Explanation: The chemical equation of burning of magnesium is given by:

$2Mg(s)+O_2(g)\rightarrow 2MgO(s)$

By stoichiometry,

2 moles of Magnesium require 1 mole of oxygen to produce 2 moles of MgO.

$\text{4 moles of Magnesium will require}=\frac{1}{2}\times 4=2\text{ moles of }O_2$

Amount of $O_2$ required to form MgO can be calculated by:

$\text{Mass of }O_2 \text{ required}=Moles\times \text{Molecular mass of }O_2$

Molecular mass of $O_2=32g/mol$

$\text{Mass of }O_2\text{ required}=2moles \times 32g/mol$

                               = 64 grams