Free cyanide in aqueous solution can be determined indirectly by atomic absorption on the basis of its ability to dissolve silver as it passes through a porous silver membrane filter at pH 12.

A series of silver standards gave a linear calibration curve in flame atomic absorption with a slope of 807 meter units per ppm Ag in the standard. (The meter units are arbitrary numbers proportional to absorbance, and ppm refers to μg Ag/mL.) An unknown cyanide solution passed through the silver membrane gave a meter reading of 198 units. Find the molarity of CN^— in the unknown.

Transcribed Image Text:

4Ag(s) + 8CN + 2H₂O + O₂ →4Ag(CN)2 + 40H-