Answer:
33.58%
Step-by-step explanation:
Data obtained from the question include:
Mass of CuS = 9.56g
Mass of Cu = 6.35g
Mass of S = Mass of CuS — Mass and Cu
Mass of S = 9.56 — 6.35
Mass of S = 3.21g
The percentage by mass of sulphur in CuS is given by:
Mass of S/mass of CuS x 100
Percentage by mass of S = 3.21/9.56 x 100 = 33.58%