4Ga + 3S2 → 2Ga2S3 1. How many grams of Gallium burned if 200.0 grams of Gallium(III)Sulfide formed?

118.4 g

Explanation:

4 Ga  +  3 S₂ → 2 Ga₂S₃

According to the equation, for every 4 moles of gallium burned, 2 moles of gallium(III) sulfide.

First, convert grams of Ga₂S₃ to moles.  The molar mass is 235.641 g/mol.

(200.0 g)/(235.641 g/mol) = 0.8487 mol

Use the relationship above to convert moles of Ga₂S₃ to moles of Ga.

(0.8487 mol Ga₂S₃) × (4 mol Ga)/(2 mol Ga₂S₃) = 1.697 mol Ga

Convert moles of Ga to grams.  The molar mass is 69.723 g/mol.

(1.697 mol Ga) × (69.723 g/mol) = 118.4 g