2. $FeS+C{{u}_{2}}S+HN{{O}_{3}}\to NO+....$
- $\overset{+2}{\mathop{Fe}}\,\overset{-2}{\mathop{S}}\,+H\overset{+5}{\mathop{N}}\,{{O}_{3}}\to \overset{+2}{\mathop{N}}\,O+\overset{+3}{\mathop{Fe}}\,{{(N{{O}_{3}})}_{3}}+{{H}_{2}}\overset{+6}{\mathop{S}}\,{{O}_{4}}+{{H}_{2}}O$
$\left. \begin{align} & \overset{+2}{\mathop{Fe}}\,\overset{-2}{\mathop{S}}\,\to \overset{+3}{\mathop{Fe}}\,+\overset{+6}{\mathop{S}}\,+9e \\ & \overset{+5}{\mathop{N}}\,+3e\to \overset{+2}{\mathop{N}}\, \\ \end{align} \right|$$\begin{align} & \times 1 \\ & \times 3 \\ \end{align}$
$\overset{+2}{\mathop{Fe}}\,\overset{-2}{\mathop{S}}\,+6H\overset{+5}{\mathop{N}}\,{{O}_{3}}\to \overset{+2}{\mathop{3N}}\,O+\overset{+3}{\mathop{Fe}}\,{{(N{{O}_{3}})}_{3}}+{{H}_{2}}\overset{+6}{\mathop{S}}\,{{O}_{4}}+2{{H}_{2}}O$(1)
- $\overset{+1}{\mathop{C{{u}_{2}}}}\,\overset{-2}{\mathop{S}}\,+H\overset{+5}{\mathop{N}}\,{{O}_{3}}\to \overset{+2}{\mathop{N}}\,O+\overset{+2}{\mathop{Cu}}\,{{(N{{O}_{3}})}_{2}}+{{H}_{2}}\overset{+6}{\mathop{S}}\,{{O}_{4}}+{{H}_{2}}O$
$\left. \begin{align} & \overset{+1}{\mathop{C{{u}_{2}}}}\,\overset{-2}{\mathop{S}}\,\to \overset{+2}{\mathop{2Cu}}\,+\overset{+6}{\mathop{S}}\,+10e \\ & \overset{+5}{\mathop{N}}\,+3e\to \overset{+2}{\mathop{N}}\, \\ \end{align} \right|$$\begin{align} & \times 3 \\ & \times 10 \\ \end{align}$
$\overset{+1}{\mathop{3C{{u}_{2}}}}\,\overset{-2}{\mathop{S}}\,+22H\overset{+5}{\mathop{N}}\,{{O}_{3}}\to \overset{+2}{\mathop{10N}}\,O+\overset{+2}{\mathop{6Cu}}\,{{(N{{O}_{3}})}_{2}}+3{{H}_{2}}\overset{+6}{\mathop{S}}\,{{O}_{4}}+8{{H}_{2}}O$(2)
Vì tỉ lệ số mol giữa $FeS$ và $C{{u}_{2}}S$là 1 : 1
Ta nhân hai vế phương trình (1) với 3 sau đó cộng từng vế hai phương trình, ta được:
$3FeS+3C{{u}_{2}}S+40HN{{O}_{3}}\to 19NO+3Fe{{(N{{O}_{3}})}_{3}}+6Cu{{(N{{O}_{3}})}_{2}}+6{{H}_{2}}S{{O}_{4}}+14{{H}_{2}}O$
2.
$\overset{+4}{\mathop{S}}\,{{O}_{2}}+K\overset{+7}{\mathop{Mn}}\,{{O}_{4}}+{{H}_{2}}O\to {{K}_{2}}\overset{+6}{\mathop{S}}\,{{O}_{4}}+\overset{+2}{\mathop{Mn}}\,\overset{+6}{\mathop{S}}\,{{O}_{4}}+{{H}_{2}}\overset{+6}{\mathop{S}}\,{{O}_{4}}$
$\left. \begin{align} & \overset{+4}{\mathop{S}}\,\to \overset{+6}{\mathop{S}}\,+2e \\ & \overset{+7}{\mathop{Mn}}\,+5e\to \overset{+2}{\mathop{Mn}}\, \\ \end{align} \right|$$\begin{align} & \times 5 \\ & \times 2 \\ \end{align}$
$\overset{+4}{\mathop{5S}}\,{{O}_{2}}+2K\overset{+7}{\mathop{Mn}}\,{{O}_{4}}+2{{H}_{2}}O\to {{K}_{2}}\overset{+6}{\mathop{S}}\,{{O}_{4}}+\overset{+2}{\mathop{2Mn}}\,\overset{+6}{\mathop{S}}\,{{O}_{4}}+2{{H}_{2}}\overset{+6}{\mathop{S}}\,{{O}_{4}}$
3.
$Na\overset{2x-1}{\mathop{I}}\,{{O}_{x}}+\overset{+4}{\mathop{S}}\,{{O}_{2}}+{{H}_{2}}O\to \overset{0}{\mathop{{{I}_{2}}}}\,+N{{a}_{2}}\overset{+6}{\mathop{S}}\,{{O}_{4}}+{{H}_{2}}\overset{+6}{\mathop{S}}\,{{O}_{4}}$
$\left. \begin{align} & \overset{+4}{\mathop{S}}\,\to \overset{+6}{\mathop{S}}\,+2e \\ & \overset{2x-1}{\mathop{2I}}\,+(4x-2)\to \overset{0}{\mathop{{{I}_{2}}}}\, \\ \end{align} \right|$$\begin{align} & \times (2x-1) \\ & \times 1 \\ \end{align}$
$2Na\overset{2x-1}{\mathop{I}}\,{{O}_{x}}+(2x-1)\overset{+4}{\mathop{S}}\,{{O}_{2}}+(2x-2){{H}_{2}}O\to \overset{0}{\mathop{{{I}_{2}}}}\,+N{{a}_{2}}\overset{+6}{\mathop{S}}\,{{O}_{4}}+(2x-2){{H}_{2}}\overset{+6}{\mathop{S}}\,{{O}_{4}}$