Question

Magnesium will burn in air to form both Mg3N2 and MgO. What mass of each product would be found if burning a 3.26 g sample of magnesium to completion produces a combined total of 5.09 g of the two products

Answer 1

Answer: The mass of MgO formed is 3.502 grams and mass of
`Mg_3N_2` formed is 1.587 grams.

Step-by-step explanation:

We are given:

Total mass of magnesium reacted = 3.26 g

Total mass of products formed = 5.09 g

To calculate number of moles of a substance, we use the equation:

`\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}` .....(1)

• For calculating mass of MgO:

The chemical equation for the formation of magnesium oxide follows:

`2Mg+O_2\rightarrow 2MgO`

Let 'x' grams of magnesium is reacting to form magnesium oxide.

Molar mass of Magnesium = 24.3 g/mol

Putting values in equation 1, we get:

Number of moles of magnesium =
`(x)/(24.3)mol`

By Stoichiometry of the reaction:

2 moles of magnesium produces 2 moles of MgO

So,
`(x)/(24.3)` moles of magnesium will produce
`(2)/(2)* (x)/(24.3)=(x)/(24.3)` moles of MgO

Molar mass of MgO = 40.3 g/mol

Putting values in equation 1, we get:

Mass of MgO =
`(x)/(24.3)* 40.3=(1.66* x)g`

Mass of magnesium oxide =
`(1.66* x)g` = X grams

• For calculating mass of
  `Mg_3N_2` :

The chemical equation for the formation of magnesium nitride follows:

`3Mg+N_2\rightarrow Mg_3N_2`

Mass of magnesium reacting = (3.26 - x)

Molar mass of Magnesium = 24.3 g/mol

Putting values in equation 1, we get:

Number of moles of magnesium =
`((3.26-x))/(24.3)mol`

By Stoichiometry of the reaction:

3 moles of magnesium produces 1 moles of
`Mg_3N_2`

So,
`((3.26-x))/(24.3)` moles of magnesium will produce
`(1)/(3)* ((3.26-x))/(24.3)=((3.26-x))/(72.9)` moles of
`Mg_3N_2`

Molar mass of
`Mg_3N_2` = 101 g/mol

Putting values in equation 1, we get:

Mass of
`Mg_3N_2=((3.26-x))/(72.9)* 101=[(3.26-x)* 1.38]g`

Mass of magnesium nitride =
`[(3.26-x)* 1.38]g` = Y grams

• Calculating the mass of products:

Total mass of the products = 5.09 grams

`X+Y=5.09`

Putting values of 'X' and 'Y' in above equation, we get:

`(1.66* x)+[(3.26-x)* 1.38]=5.09\\\\x=2.11g`

Mass of MgO =
`(1.66* 2.11)=3.502g`

Mass of
`Mg_3N_2=[(3.26-2.11)* 1.38]=1.587g`

Hence, the mass of MgO formed is 3.502 grams and mass of
`Mg_3N_2` formed is 1.587 grams.