10.0dm³ of air confirming H₂S as an impurity was passed through a soultion of Pb(NO₃) until all the H₂S had reacted. The precipitate of PbS was found to weigh 5.02g. According to the equation,
Pb(NO₃) + H₂S --> PbS + HNO₂
the percentage by volume of hydrogen sulphide
(Pb = 207, S = 32, GMC at A.T.P. = 22.4dm³)

• A.50.2
• B.47.0
• C.4.70
• D.0.47