Question

Lithium and nitrogen react in a combination reaction to produce lithium nitride: 6Li (s) + N2 (g) → 2Li3N (s) In a particular experiment, 4.00-g samples of each reagent are reacted. The theoretical yield of lithium nitride is ________ g.

Answer 1

6.69 g.

Explanation

Make sure the chemical equation is balanced:

$6\; \text{Li}\; (s) + \text{N}_2 \; (g) \to 2\; \text{Li}_3\text{N}\; (s)$

Assuming that one mole of N₂ is consumed. How many grams of each reactant will that take? Refer to a periodic table for data on atomic mass.

• 6 × 6.94 = 41.64 grams of Li;
• 1 × (2 × 14.01) = 28.02 grams of N₂.

4.00 grams of each reactant are available. How many moles of N₂ can they consume?

• 4.00 grams of Li will lead to up to 4.00 / 41.64 = 0.09606 moles of the reaction.
• 4.00 grams of N₂ will lead to up to 4.00 / 28.02 = 0.1428 moles of the reaction.

However, only 0.09606 moles of the reaction is possible, since Li would have ran out before all 4.00 grams of N₂ are used up.

Each mole of the reaction makes 2 moles of Li₃N. 0.09606 moles of the reaction will produce 0.09606 × 2 × (3 × 6.94 + 14.01) = 6.69 grams of Li₃N.