Question

Given the reaction below, how many grams of Li3N can be formed from 6.07 g of Li? Assume an excess of nitrogen.

Answer 1

Answer:

About 10.2 g Li₃N.

Explanation:

We are given the reaction:

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

And we want to determine the amount of Li₃N that can be formed from 6.07 g of Li and an excess of nitrogen.

To convert from g Li to g Li₃N, we can: (1) convert from g Li to mol Li, (2) mol Li to mol Li₃N, and (3) mol Li₃N to g Li₃N.

1. The molecular weight of Li is 6.94 g/mol.
2. From the equation, six moles of Li yields two moles of Li₃N.
3. And the molecular weight of Li₃N is 34.83 g/mol as shown below.

Molecular weight of Li₃N:

$\displaystyle \begin{aligned}\text{MW}_\text{Li _3 N} & = (3 (6.94) + 14.01) \text{ g/mol} \\ \\ & =34.83\text{ g/mol} \end{aligned}$

This yields three ratios:

$\displaystyle \frac{1 \text{ mol Li}}{6.94 \text{ g Li}}, \frac{2 \text{ mol Li _3 N}}{6 \text{ mol Li}}, \text{ and } \frac{34.83 \text{ g Li _3 N}}{1 \text{ mol Li _3 N}}$

From the initial value, multiply:

$\displaystyle 6.07 \text{ g Li} \cdot \frac{ 1 \text{ mol Li}}{6.94 \text{ g Li}} \cdot \frac{2 \text{ mol Li _3 N}}{6 \text{ mol Li}} \cdot \frac{34.83 \text{ g Li _3 N}}{1 \text{ mol Li _3 N}} = 10.2\text{ g Li _3 N}$

In conclusion, 10.2 g of Li₃N is formed from 6.07 g of Li and an excess of nitrogen.