Question

When 0.0976g of magnesium was heated in air, 0.1618g of magnesium oxide (MgO) was produced. What is the mass of oxygen needed to produce 0.1618g MgO?

Answer 1

Answer:

Magnesium reacts with oxygen to produce magnesium oxide:

2Mg(s) + O2(g) 2MgO(s)

Calculate the mass of magnesium needed to produce 12.1g of magnesium oxide.

(Relative masses: Mg = 24.3, MgO = 40.3)

number of moles of MgO =

=

= 0.300 mol.

Answer 2

The mass of oxygen needed to produce 0.1618g MgO is 0.65 g

When Mg is heated in air, it mainly reacts with nitrogen and oxygen .

With reaction of O₂, Mg forms MgO.

The reaction is as follow:

2 Mg₍s₎ + O₂₍g₎ ⇄  2 MgO₍s₎

The molecular weight of Mg = 24 g

                         O₂ = (2 × 16) g

                               = 32 g

                         MgO = (24 + 16) = 40 g

Given,

0.0976 g Mg gives 0.1618 g MgO

Now, from the reaction, we get

(2×40) = 80 g of MgO reacts with 32 g of  O₂

or,  0.1618 g MgO reacts with  $\frac{32}{80}$ × 0.1618 g  O₂

                                           = 0.6472 g  O₂

And,

(2×24) = 48 g of Mg reacts with 32 g of  O₂

or,  0.0976 g Mg reacts with  $\frac{32}{48}$ × 0.0976 g  O₂

                                           = 0.06500 g  O₂

So, the oxygen needed is 0.65 g (approximately)