Question

Ethene is formed when ethanol at 443 K is heated with excess concentrated sulphuric acid. What is the role of sulphuric acid in this reaction? Write the balanced chemical equation of this reaction.

Answer 1

Dehydrating Agent:

• A chemical compound used to drive a dehydration reaction
• In chemical reactions where dehydration occurs, the reacting molecule loses a molecule of water.
• Sulfuric acid, concentrated phosphoric acid, hot aluminium oxide, and hot ceramic are common dehydrating agents in these types of chemical reactions.

Dehydration of ethanol

• When ethanol is heated to 443K in the presence of hot concentrated H₂SO₄, which functions as a catalyst in this reaction, an unsaturated molecule, ethene (${\mathrm{CH}}_2={\mathrm{CH}}_2$) is produced
• Dehydration of alcohol in presence of dehydrating agents produces alkene and water.

$$\begin{gathered} {\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{OH}\underset{}{\overset{}{\left(\mathrm{aq}\right)\underset{443\mathrm{K}}{\overset{{\mathrm{H}}_2{\mathrm{SO}}_4}{\to }}}}{\mathrm{H}}_2\mathrm{C}={\mathrm{CH}}_2\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{ethanol}\mathrm{ethene}\mathrm{water} \end{gathered}$$

• In the formation of ethene, sulphuric acid functions as a catalyst and a dehydrating agent as it removes water from ethanol.