# Sometimes yellow turbidity appears while passing $H_2S$ gas even in the absence of II group radicals. This is because

(a) Sulphur is present in the mixture as impurity
(b) IV group radicals are precipitated as sulphides
(c) of the oxidation of $H_2S$ gas by some acid radical
(d) III group radicals are precipitated as hydroxide

Answer:  of the oxidation of $H_2S$ gas by some acid radical

$H_2S + [O] \longrightarrow S\downarrow + H_2O$
(For some  (Colloidal Sulphur)
edited Jan 29, 2014