To determine the chloride content of an unknown soluble chloride salt, a student dissolves 0.4250 g of the salt in water and adds excess 0.10 M AgNO3. A white precipitate forms, which is filtered onto pre-weighed filter paper, washed with cold water, and dried to constant mass. Mass of dried precipitate = 0.8610 g.
What is the purpose of using excess AgNO3?
- Acheck_circle
To ensure complete precipitation of all Cl- as AgCl
- B
To form a more soluble silver complex
- C
To decrease the molar mass of the precipitate
- D
To buffer the solution at a fixed pH
Explanation
Excess Ag+ drives the precipitation of Cl- to completion (very small Ksp of AgCl) so that the gravimetric analysis is quantitative.