What mass of solid CaO is needed to remove the sulfur dioxide from 1.0 × 10⁶ m³ of air having an SO₂ concentration of 1.5 × 10^-9 M? Assume that the reaction leading to removal of the sulfur dioxide is CaO(s)+ SO₂(g)$\rarr$CaCO₃(s).

Question

Quizplus · Accepted Answer

The first step is to calculate the number of moles of SO2 in the given volume of air:
n(SO2) = (1.0 × 10-16 mol/L) x (1.5 × 10-9 M) x (1 L/1000 mL) = 1.5 × 10-26 mol
According to the stoichiometry of the reaction, 1 mol of CaO reacts with 1 mol of SO2, so the mass of CaO needed is:
m(CaO) = n(CaO) x M(CaO) = n(SO2) x M(CaO)
M(CaO) = 56.08 g/mol
m(CaO) = (1.5 × 10-26 mol) x (56.08 g/mol) = 8.41 × 10-25 g
Round this answer to two significant figures: 8.4 × 10-25 g ≈ 84 g.

What Mass of Solid CaO Is Needed to Remove the Sulfur