Question

The mineral orpiment, having the empirical formula As2S3, was used in ancient times as a cosmetic. What mass of arsenic is present in 5.0 g of orpiment? Hint: Determine the percent composition of As in As2S3 , then take that percent of 5.0 g.

Answer 1

Answer : The mass of arsenic present in 5.0 g of orpiment is, 1.5 grams.

Explanation : Given,

Mass of orpiment = 5.0 g

As we know that the molar mass of
`As_2S_3` is, 246.02 g/mol and the molar mass of As is, 75 g/mol.

As per the question, we conclude that:

As, 246.02 g of
`As_2S_3` contains mass of arsenic = 75 g

So, 5.0 g of
`As_2S_3` contains mass of arsenic =
`(5.0)/(246.02)* 75=1.5g`

Thus, the mass of arsenic present in 5.0 g of orpiment is, 1.5 grams.