Lithium reacts with nitrogen gas according to the following reaction: 6Li(s)+N2(g)→2Li3N(s) What mass of lithium (in g ) reacts completely with 72.9 mL of N2 gas at STP?

Answer 1

6Li(s) + N₂(g) ==> 2Li₃N(s) ... balanced equation

At STP, 1 mole of any ideal gas = 22.4 L

Finding moles of N₂, we have

72.9 ml N₂ x 1 L / 1000 ml x 1 mol / 22.4 L = 0.00325 moles N₂

From the balanced equation, it takes 6 mols Li for each 1 mol of N₂. Finding moles Li needed, we have

0.00325 mol N₂ x 6 mol Li / mol N₂ = 0.0195 moles Li needed

Converting moles of Li to grams of Li using the atomic mass of Li (6.94 g/ mol), we have

0.0195 mols Li x 6.94 g / mol = 0.135 g Li