Question

Ordinarily, elemental nitrogen gas is not very reactive. However, when one of the more reactive

metallic elements is heated in pure nitrogen, nitrogen is reduced to the nitride ion, N³. For example,
when magnesium metal is heated in pure nitrogen, magnesium nitride results.
3Mg(s) + N2(g) -- Mg N₂(s)

a.
What mass of N2 is needed to completely react 20 grams of Mg.

b. How much Mg3N2 is produced?

Answer 1

a. The balanced chemical equation for the reaction between Mg and N2 is:

3Mg(s) + N2(g) → Mg3N2(s)

From the equation, we can see that 3 moles of Mg reacts with 1 mole of N2 to produce 1 mole of Mg3N2. The molar mass of Mg is 24.31 g/mol, while the molar mass of N2 is 28.02 g/mol. To determine the mass of N2 required to react with 20 g of Mg, we can use the following calculation:

20 g Mg × (1 mol Mg/24.31 g) × (1 mol N2/3 mol Mg) × (28.02 g N2/1 mol N2) = 30.4 g N2

Therefore, 30.4 g of N2 is needed to completely react with 20 g of Mg.

b. Using the same balanced chemical equation as in part (a), we can see that 3 moles of Mg react to form 1 mole of Mg3N2. The molar mass of Mg3N2 is 100.93 g/mol. To determine the mass of Mg3N2 produced, we can use the following calculation:

20 g Mg × (1 mol Mg/24.31 g) × (1 mol Mg3N2/3 mol Mg) × (100.93 g Mg3N2/1 mol Mg3N2) = 83.4 g Mg3N2

Therefore, 83.4 g of Mg3N2 is produced from 20 g of Mg.