Đáp án:
(1) $\underbrace {2H_{2}S}_{\text{C. khử}}+ \underbrace{O_{2\ \text{thiếu}}}_{\text{C. oxi hóa}} → 2S +2H_{2}O$
(2) $\underbrace{S}_{\text{C. oxi hóa}} +\underbrace {Fe}_{\text{C. khử}} \buildrel{{t^o}}\over\longrightarrow FeS$
(3) $FeS +2HCl → FeCl_{2} +H_{2}S$
(4) $\underbrace {H_{2}S}_{\text{C. khử}} +\underbrace{O_{2}}_{\text{C. oxi hóa}} \buildrel{{t^o}}\over\longrightarrow SO_{2} + H_{2}O$
(5) $\underbrace {SO_{2}}_{\text{C. khử}}+\underbrace{Br_{2}}_{\text{C. oxi hóa}} +H_{2}O → H_{2}SO_{4} +2 HBr$
(6) $\underbrace {2SO_{2}}_{\text{C. khử}} +\underbrace{O_{2}}_{\text{C. oxi hóa}} \buildrel{{V_2O_5,t^o}}\over\longrightarrow 2SO_{3}$
(7) $SO_{3} + H_{2}O→ H_{2}SO_{4}$
(8) $\underbrace{6H_{2}SO_{4}}_{\text{C. oxi hóa}} + \underbrace {2Fe}_{\text{C. khử}} → Fe_2(SO_4)_3 + 3SO_{2} + 6H_{2}O$
(9) $\underbrace{SO_{2}}_{\text{C. oxi hóa}} +\underbrace {2H_{2}S}_{\text{C. khử}} → 3S +2H_{2}O$
