Answer:
78.9 g Si would need to react with excess nitrogen
Explanation:
The reaction that takes place is:
3Si + 2N₂ → Si₃N₄
Keeping in mind the yield, we can calculate the required moles of Si, using the mass of silicon nitride and its molar mass (140 g/mol):
125 g Si₃N₄ ÷ 140 g/mol = 0.893 mol Si₃N₄
0.893 mol Si₃N₄ * 100/95.0 * [tex]\frac{3molSi}{1molSi_{3}N_{4}}[/tex] = 2.82 mol Si
Finally we convert the moles of Si to g:
2.82 mol Si * 28 g/mol = 78.9 g Si
