Throughout history, arsenic(III) oxide, known simply to the general public as "arsenic," has been a poison favored by murderers: It is tasteless, colorless, can be easily added to food or drink, produces symptoms that are similar to several diseases, and until the mid-1800s, was undetectable in the body. James Marsh developed the famous "Marsh test" for arsenic that was instrumental in convicting the murderer in a famous poisoning case in France in 1840. The Marsh test relies on the reaction of arsenic(III) oxide in a sample with elemental zinc and sulfuric acid to produce arsine (an analog of ammonia), zinc sulfate, and water. Upon igniting the final mixture, arsine is oxidized to elemental arsenic, and if captured on a ceramic bowl, a characteristic silvery-black powder would appear.

(a) Write the balanced chemical equations of the Marsh test.

(b) Antimony is the only potential interferent, as it reacts similarly to arsenic and produces a similar silvery-black film; however, antimony does not dissolve in a solution of sodium hypochlorite, but arsenic does. Therefore, the completion of the Marsh test is to add a solution of sodium hypochlorite to the elemental arsenic and see if the silvery-black film dissolves. Write the balanced chemical equation for this final reaction.

(c) Today, commercial kits for arsenic testing rely on a different reaction. The sample is reacted with hydrogen sulfide in the presence of hydrochloric acid; if arsenic is present,As2S3,which is a bright yellow precipitate, forms. Write the balanced equation for this reaction.