\(10.0 dm ^{3}\) of air containing \(H _{2} S\) as an impurity was passed through a solution of \(Pb \left( NO _{3}\right)\) until all the \(H _{2} S\) had reacted. The precipitate of \(PbS\) was found to weigh \(5.02 g\). according to the equation, \(Pb \left( NO _{3}\right)_{2}+ H _{2} S \rightarrow PbS +\) \(2 HNO _{3}\) the percentage by volume of hydrogen sulphide (Pb =207, \& \(4.32 GM 7 .\) at STP \(=22.4 dm ^{3}\) )
