Question

he toxic gas hydrogen fluoride, HF, is produced from the double displacement reaction of calcium fluoride, CaF₂, and concentrated sulfuric acid, H₂SO₄. Starting with 10.0g of CaF₂ and 15.0g H₂SO₄, the balanced chemical equation is CaF₂ + H₂SO₄ → 2 HF + CaSO₄.Which is the excess reactant?

Answer 1

M(CaF₂) = 78.07 g/mol

n(CaF₂) $= \frac{10.0}{78.07} = 0.128 \;mol$

M(H₂SO₄) = 98.08 g/mol

n(H₂SO₄) $= \frac{15.0}{98.08} = 0.153 \;mol$

According to the reaction for one mole of CaF₂ we need one mole of H₂SO₄.

0.128<0.153

So, CaF₂ is the limiting reactant.