Q.64. - Organic Chemistry

Question

Question: Draw the products of combustion of each alkane.

a.

b.

Step-by-Step Solution

Answer

Answer

$$\begin{gathered} a. 7C{O}_2 and 8H_{2}O \\ b. 4C{O}_2 and 5H_{2}O \end{gathered}$$

Step 1: Combustion reaction

In a combustion reaction, a substance burns in the presence of oxygen (excess of air) to give carbon dioxide gas and water as the only reaction products.

The products of combustion reactions always remain the same irrespective of the reactant materials. The initial substance undergoing the combustion reaction is generally called a fuel.

Step 2: Combustion of alkanes

Combustion requires a flame or spark for the initiation of the reaction. 

When alkanes undergo combustion, all of their C-H bonds and C-C bonds break to form new C-O bonds.

Step 3: Combustion reactions of the given alkanes

a. The given compound 2-methylhexane reacts with the oxygen in the air to give seven moles of carbon dioxide gas and eight moles of water.

$$\begin{gathered} C{H}_3-C{H}_2-C{H}_2-C{H}_2-CH{\left(C{H}_3\right)}_2 + 11O_2 \stackrel{Flame}{\to }7C{O}_2+8H_{2}O \\ \left(2-methylhexane\right) \end{gathered}$$

b. The given compound butane undergoes combustion to form four moles of carbon dioxide gas and five moles of water.

$C{H}_3-C{H}_2-C{H}_2-C{H}_3 + \frac{13}{2}{O}_2 \stackrel{Flame}{\to }4C{O}_2+5H_{2}O$