Assessment And Qualifications Alliance (AQA) GCSE Biology Paper 2 Practice Exam

Alkenes react with water through a process known as hydration, and the reaction requires specific conditions to proceed effectively. The correct conditions involve using steam at high temperatures, typically around 300°C, in the presence of a catalyst, often phosphoric acid or sulfuric acid. The high temperature is essential because it provides the energy needed to help break the double bond between the carbon atoms in the alkene, allowing the water molecules to add across the double bond and form an alcohol. The catalyst further accelerates the reaction without being consumed in the process, facilitating the conversion of the alkene into the corresponding alcohol more efficiently. In contrast, cold water with a catalyst is generally not effective for alkene hydration, as lower temperatures do not provide enough energy for the reaction to occur at a practical rate. Similarly, room temperature conditions lack both the necessary energy and the appropriate catalyst setup to ensure that hydration takes place effectively. Lastly, while hot water may seem beneficial, it is insufficient without a catalyst and does not provide the right conditions for the reaction to occur at a significant rate. Thus, steam under high temperature and in the presence of a catalyst is critical for the successful reaction of alkenes with water.