How many grams of Li3N can be formed from 12.1 grams of Li? Assume an excess of nitrogen (N2). 6 Li(s) + N2(g) → 2 Li3N(s)

Question

Formula: 6 Li(s) + N2(g) → 2 Li3N(s)

Answer 1

In order to determine the mass of Li₃N that we could form, we first need to determine which reactant is limiting. Our reactants are lithium metal and nitrogen gas. We have an excess of nitrogen gas, so our limiting reactant will be lithium metal.

In order to determine the mols of Li₃N that can form, we must determine the moles of lithium available. We can convert mass of lithium to moles of lithium via the atomic mass of lithium:

12.1g Li (1 mol / 6.941g) = 1.74 mol Li

Next we examine the balanced equation. We can see that for every 6 mols of Lithium metal that reacts, 2 mols of Li₃N will form. Using this info, we can convert moles of Li to moles Li₃N:

1.74 mol Li (2 mol Li₃N / 6 mol Li) = 0.581 mol Li₃N

Finally we can convert mol Li₃N to grams using the molar mass of Li₃N. We can determine the molar mass using the atomic masses from the periodic table:

molar mass of Li₃N = 3 * atomic mass lithium + 1 * atomic mass nitrogen = 3 * 6.941 + 1 * 14.01 = 34.8 g/mol

We can use this to convert moles to grams:

0.581 mol Li₃N (34.8 g / mol) = 20.2g Li₃N