Arsenic is often obtained by heating the ore arsenopyrite, FeAsS. The decomposition of FeAsS is represented by the balanced equation below.

FeAsS(s) ==heat==>FeS(s) + As(g)

In the solid phase, arsenic occurs in two forms. One form, yellow arsenic, has a density of 1.97 g/cm3 at STP. The other form, gray arsenic, has a density of 5.78 g/cm3 at STP. When arsenic is heated rapidly in air, arsenic(III) oxide is formed. Although arsenic is toxic, it is needed by the human body in very small amounts. The body of a healthy human adult contains approximately 5 milligrams of arsenic.

79 Convert the mass of arsenic found in the body of a healthy human adult to grams.