A quality control technician needs to determine the percentage of arsenic (As) in a particular pesticide. The pesticide is dissolved, and all of the arsenic present is converted to arsenate ions (AsO₄ ^3-). Then the amount of AsO₄ ^3- is determined by titrating with a solution containing silver ions (Ag⁺). The silver reacts with the arsenate according to the following net ionic equation:

When a 1.22-g sample of pesticide was analyzed this way, it required 25.0 mL of 0.102 M Ag⁺ solution to precipitate all of the AsO4 ^3-. What was the mass percentage of arsenic in the pesticide?

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3 Ag+ (aq) + AsO4³ (aq) → Ag-AsO4(s)