Question

consider this reaction:
li₃n (s) + 3h₂o (l) → nh₃ (g) + 3lioh (l)
you need to make 240 g lioh. how many grams of li₃n (s) must you react with excess water?
1050 g
700 g
117 g
350 g

Explanation:

Step1: Calculate moles of LiOH

Molar mass of LiOH: Li (6.94 g/mol) + O (16.00 g/mol) + H (1.01 g/mol) = 23.95 g/mol.
Moles of LiOH = $\frac{240\ g}{23.95\ g/mol} \approx 10.02\ mol$.

Step2: Relate moles of LiOH to Li₃N

From the reaction: 1 mol Li₃N produces 3 mol LiOH.
Moles of Li₃N = $\frac{10.02\ mol\ LiOH}{3} \approx 3.34\ mol$.

Step3: Calculate mass of Li₃N

Molar mass of Li₃N: 3×6.94 + 14.01 = 34.83 g/mol.
Mass of Li₃N = $3.34\ mol × 34.83\ g/mol \approx 117\ g$.

Answer:

117 g (corresponding to the option "117 g")