Chemistry Question

Question

One of the commercial uses of sulfuric acid is in the production of calcium sulfate and phosphoric acid. If 25.4 g of Ca₃(PO₄)₂ reacts with an excess of H₂SO₄, what is the percent yield if 13.4 g of H₃PO₄ are formed in the following UNBALANCED chemical equation? Ca₃(PO₄)₂ (s) + H₂SO₄ (aq) → H₃PO₄ (aq) + CaSO₄ (aq)

Answer 1

Ca₃(PO₄)₂ (s) + H₂SO₄ (aq) → H₃PO₄ (aq) + CaSO₄ (aq)

Balanced: Ca₃(PO₄)₂ (s) + 3 H₂SO₄ (aq) → 2 H₃PO₄ (aq) + 3 CaSO₄ (aq)

Ca₃(PO₄)₂ is 310.17 g/mol, so 25.4 g is 0.0819 mol.

Since the ratio of Ca₃(PO₄)₂ to H₃PO₄ in our balanced equation is 2:1, we would expect to get out (0.0819 mol)*2, or 0.164 mol. H₃PO₄ is 97.99 g/mol, so we would get about 16.07 g. However, we only have 13.4 g.

Percent yield is 100*(actual yield)/(theoretical yield). 100*(13.4 g/16.04 g) = 83.54% yield.