A 0.500 g sample of an impure solid thought to be Na₂CO₃ is dissolved in water and titrated with 0.150 M HCl. The endpoint is reached after 28.0 mL of the acid has been added. The relevant net ionic equation is
2 H⁺(aq) + CO₃²⁻(aq) → CO₂(g) + H₂O(l)
What is the percent purity of Na₂CO₃ in the sample? (Molar mass Na₂CO₃ = 106 g·mol⁻¹)
a) 25.2%
b) 88.9%
c) 44.5%
d) 55.5%