Lithium reacts with nitrogen gas according to the following reaction:

[tex]\[
6 \, \text{Li} (s) + \text{N}_2 (g) \rightarrow 2 \, \text{Li}_3 \text{N} (s)
\][/tex]

What mass of lithium is required to react completely with 58.9 mL of [tex]\(\text{N}_2\)[/tex] gas at STP?

Express your answer in grams.



Answer :

Let's solve this problem step-by-step to determine the mass of lithium required to react completely with 58.9 mL of [tex]\( N_2 \)[/tex] gas at standard temperature and pressure (STP).

1. Convert the volume of [tex]\( N_2 \)[/tex] gas from mL to L:

Given:
[tex]\[ \text{Volume of } N_2 = 58.9 \text{ mL} \][/tex]

Since 1 L = 1000 mL, we convert mL to L:
[tex]\[ \text{Volume of } N_2 = \frac{58.9 \text{ mL}}{1000} = 0.0589 \text{ L} \][/tex]

2. Calculate the moles of [tex]\( N_2 \)[/tex] gas using the molar volume at STP:

At STP, 1 mole of any gas occupies 22.414 L. Therefore, the number of moles of [tex]\( N_2 \)[/tex] can be calculated using:
[tex]\[ \text{Moles of } N_2 = \frac{\text{Volume of } N_2}{\text{Molar volume at STP}} = \frac{0.0589 \text{ L}}{22.414 \text{ L/mol}} = 0.0026278218970286426 \text{ mol} \][/tex]

3. Determine the moles of [tex]\( Li \)[/tex] required using the stoichiometric ratio from the balanced chemical equation:

The balanced chemical reaction is:
[tex]\[ 6 Li (s) + N_2(g) \rightarrow 2 Li_3N(s) \][/tex]

This tells us that 1 mole of [tex]\( N_2 \)[/tex] reacts with 6 moles of [tex]\( Li \)[/tex]. So, the moles of [tex]\( Li \)[/tex] required can be calculated as follows:
[tex]\[ \text{Moles of } Li = 0.0026278218970286426 \text{ mol} \times 6 = 0.015766931382171855 \text{ mol} \][/tex]

4. Calculate the mass of [tex]\( Li \)[/tex] required:

The molar mass of lithium [tex]\( (Li) \)[/tex] is 6.94 g/mol. To find the mass of lithium required, we multiply the number of moles of [tex]\( Li \)[/tex] by its molar mass:
[tex]\[ \text{Mass of } Li = 0.015766931382171855 \text{ mol} \times 6.94 \text{ g/mol} = 0.10942250379227268 \text{ g} \][/tex]

Therefore, the mass of lithium required to react completely with 58.9 mL of [tex]\( N_2 \)[/tex] gas at STP is approximately 0.109 grams.