The presence of arsenic in a sample that may also contain another Group 5A element, antimony, can be confirmed by first precipitating the As³⁺ and Sb³⁺ ions as yellow solid As₂S₃ and orange solid Sb₂S₃. If aqueous HCl is then added, only Sb₂S₃ dissolves, leaving behind solid As₂S₃. The As₂S₃ can then be dissolved using aqueous HNO₃.

Finally, the presence of arsenic is confirmed by adding AgNO₃ to the solution of H₃AsO₄ to precipitate a reddish brown solid Ag_xAsO_y. The composition of this solid is As, 16.199% and Ag, 69.964%.

(a) What are the oxidation numbers of As, S, and N in the reaction of As₂S₃ with nitric acid?
(b) What is the formula of the reddish brown solid Ag_xAsO_y?

Transcribed Image Text:

3 As₂S3 (s) + 10 HNO3(aq) + 4 H₂O(l) → 6 H3ASO4(aq) + 10 NO(g) + 9 S(s)