Calculate the mass of a 20% sodium hydroxide solution required to fully precipitate iron ions from 200 ml of a 0.5 M iron(III) chloride solution.
- 20 g
- 40 g
- 60 g
- 80 g
📝 Detailed explanation
FeCl₃ + 3NaOH → Fe(OH)₃ + 3NaCl.Moles FeCl₃ = 0.2 L × 0.5 M = 0.1 mol.
Moles NaOH needed = 0.1 × 3 = 0.3 mol.
Mass of NaOH = 0.3 × 40 = 12 g.
Mass of 20% solution = 12 / 0.20 = 60 g.