This question is about alkenes and alcohols - AQA - GCSE Chemistry - Question 10 - 2021 - Paper 2

The conditions for producing ethene through cracking typically involve high temperatures in the range of 300 to 900 °C and the presence of steam or a catalyst. The use of a catalyst can further enhance the reaction rate and efficiency.

To produce ethanol economically from ethene and steam, a balance must be struck between the reaction rate and yield. Higher temperatures increase the rate but also reduce yield due to the exothermic nature of the reaction. Thus, a moderate temperature should be chosen to optimize both the reaction speed and product formation. Additionally, using a catalyst can lower the activation energy required, allowing the reaction to proceed faster without needing excessively high temperatures. Lastly, increasing pressure can also drive the equilibrium towards ethanol production.

The process used to produce ethanol from sugar by adding yeast is called fermentation.

To produce butanol from sugar solution using bacteria, the conditions should be warm, typically between 25 °C and 45 °C, and anaerobic, meaning that oxygen should be excluded to favor butanol production instead of other byproducts.

To calculate the number of moles of ethanol needed for the car to travel 200 km:

1. Convert distance to meters: 200 km = 200,000 m.

2. Calculate the energy needed:

   Energy required = distance × energy per meter = 200,000 m × 1.95 kJ/m = 390,000 kJ.

3. Since ethanol has an energy content of 1300 kJ/mol, the number of moles required is:

   Moles of ethanol = Total energy required / Energy content per mole = 390,000 kJ / 1300 kJ/mol = 300 mol.

The balanced equation for the complete combustion of butanol (C₄H₁₀O) is:

C₄H₁₀O + 6 O₂ → 4 CO₂ + 5 H₂O.