Question

The molar mass of O2 is 32.0 g/mol. What mass, in grams, of O2 is required to reach completely with 4.00 mol of Mg

Answer 1

The reaction is as follows:

2Mg + O2 ➡️ 2MgO

Four moles of Magnesium means that the reaction can be run twice before it is depleted; two moles of O2 are required to react with this amount of Magnesium, as per the stoichiometric coefficients.

2 mol x 32 g/mol = 64 g O2 required.

Answer 2

Answer : The mass of $O_2$ required is 256 grams.

Explanation :

The balanced chemical reaction will be:

$2Mg+O_2\rightarrow 2MgO$

First we have to calculate the moles of $O_2$.

From the balanced reaction we conclude that,

As, 2 moles of Mg react with 1 mole of $O_2$

So, 4.00 moles of Mg react with $4.00\times 2=8.00$ mole of $O_2$

Now we have to calculate the mass of $O_2$.

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

Molar mass of $O_2$ = 32.0 g/mole

$\text{ Mass of }O_2=(8.00moles)\times (32.0g/mole)=256g$

Therefore, the mass of $O_2$ required is 256 grams.