Identify the oxidizing and reducing agents in the following:

$$\begin{gathered} \left(a\right)Sn\left(s\right)+2H^{+}\left(aq\right)\to S{n}^{2+}\left(aq\right)+H_2\left(g\right) \\ \left(b\right)2H^{+}\left(aq\right)+H_2{O}_2\left(aq\right)+2F{e}^{2+}\left(aq\right)\to 2F{e}^{3+}\left(aq\right)+2H_{2}O\left(l\right) \end{gathered}$$

The oxidation state of element tin is 0.

Oxidation state of tin in Sn²⁺ is +2.

Oxidation state of Hydrogen is +1.

Let, oxidation state of oxygen in H₂O₂ is x.

Now you can write,

^{$$\begin{gathered} 2\left(+1\right)+2x=0 \\ 2x=-2 \\ x=-1 \end{gathered}$$}

Oxidation state of Hydrogen is +1.

Let, oxidation state of oxygen in H₂O is y.

Now you can write,

^{$$\begin{gathered} 2\left(+1\right)+y=0 \\ y=-2 \end{gathered}$$}

In the given reaction

$Sn\left(s\right)+2H^{+}\left(aq\right)\to S{n}^{2+}\left(aq\right)+H_2\left(g\right)$

The oxidation state of tin in Sn is 0 which increases to +2 in Sn²⁺. Therefore, Sn undergoes oxidation in this given reaction. Hence, it acts as a reducing agent.

The oxidation state of oxygen in H₂O₂ is -1 which reduces to -2 in H₂O. Therefore, H₂O₂undergoes reduction in this given reaction. Hence, it acts as an oxidizing agent.

Oxidation state of iron in Fe²⁺ is +2.

Oxidation state of iron in Fe³⁺ is +3.

Oxidation state of Hydrogen is +1.

Let, oxidation state of oxygen in H₂O₂ is x.

Now you can write,

^{$$\begin{gathered} 2\left(+1\right)+2x=0 \\ 2x=-2 \\ x=-1 \end{gathered}$$}

Oxidation state of Hydrogen is +1.

Let, oxidation state of oxygen in H₂O is y.

Now you can write,

^{$$\begin{gathered} 2\left(+1\right)+y=0 \\ y=-2 \end{gathered}$$}

In the given reaction

$2H^{+}\left(aq\right)+H_2{O}_2\left(aq\right)+2F{e}^{2+}\left(aq\right)\to 2F{e}^{3+}\left(aq\right)+2H_{2}O\left(l\right)$

The oxidation state of iron in Fe²⁺ is +2 which increases to +3 in Fe³⁺. Therefore, Fe²⁺ undergoes oxidation in this given reaction. Hence, it acts as a reducing agent.

The oxidation state of oxygen in H₂O₂ is -1 which reduces to -2 in H₂O. Therefore, H₂O₂undergoes reduction in this given reaction. Hence, it acts as an oxidizing agent.