International General Certificate of Secondary Education (IGCSE) Chemistry Practice Exam

What conditions are needed for the dehydration of ethanol to ethene?

1. Low temperature and pressure

2. Hot aluminum oxide catalyst

3. Cooled aluminum oxide catalyst

4. High pressure and oxygen

The correct answer is: Hot aluminum oxide catalyst

The dehydration of ethanol to ethene requires specific conditions to promote the reaction effectively. The use of a hot aluminum oxide catalyst provides the necessary energy to facilitate the elimination of water from ethanol. Aluminum oxide (Al2O3) is commonly utilized in this dehydration process, as it can assist in breaking the bonds in ethanol and forming ethene while releasing water. In the presence of heat, the reaction not only becomes more favorable, but the hot catalyst also increases the rate of reaction by providing an optimal surface for the reaction to occur. This enhances the chances for ethanol molecules to interact with the catalyst and convert to ethene, making it a crucial step in the process. Other options, such as low temperature and pressure, or a cooled catalyst, do not sufficiently drive the reaction forward. These conditions would slow down the reaction and may not provide enough energy to overcome the activation energy barrier required for dehydration. High pressure and oxygen do not directly facilitate the transformation of ethanol to ethene in this context, making them unsuitable for this reaction as well.