Q4.85P - Chemistry: Molecular Nature Of Matter And Change

Question

Are all combustion reactions redox reactions? Explain

Step-by-Step Solution

Answer

You need to explain that all the combustion reactions are redox reactions.

Step 1: General Combustion Reaction

$2CO\left(g\right)+O_2\left(g\right)\to 2C{O}_2\left(g\right)$

Step 2: Oxidation of carbon in CO

Oxidation no of oxygen is -2.

Let assume, oxidation no of carbon in CO is x.

Now you can write,

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

Step 3: Oxidation no of carbon in CO 2

Oxidation no of oxygen is -2.

Let assume, oxidation no of carbon in CO₂ is y.

Now you can write,

 $$\begin{gathered} y+2\left(-2\right)=0 \\ y=+4 \end{gathered}$$$$\begin{gathered} y+2\left(-2\right)=0 \\ y=+4 \end{gathered}$$

Step 4: Oxidation no of oxygen

The oxidation no of oxygen in O₂ is 0.

The oxidation no of oxygen in CO₂ is -2.

Step 5: Conclusion

In a combustion reaction,

The oxidation no of oxygen is 0 in O₂ decreases to -2 in CO₂. Therefore, O₂ undergoes reduction.

The oxidation no of carbon is +2 in CO increases to +4 in CO₂. Therefore, CO undergoes oxidation.

Hence, all combustion reactions are redox reaction.