Determine the mass of Ga₂O₃ formed from the reaction of 14.5 g gallium metal with excess O₂.

Strategy

Solve the problem by using the four-step procedure just outlined:

(1) Write the balanced equation;

(2) Calculate the moles of the given substance, gallium, from the mass;

(3) Use the chemical equation to calculate the moles of desired species, Ga₂O₃, from the moles of gallium;

(4) Finish the problem by calculating the mass of Ga2O3 from the moles of Ga₂O₃. The information needed for steps 2 and 4 comes from the periodic table and the chemical formulas, and step 3 from the coefficients in the equation. Because the oxygen is in excess, the amount of product formed will depend only on the amount of the gallium.