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

The conditions used to produce ethene from large hydrocarbon molecules typically include high temperatures, usually in the range of 300 to 900 °C, along with the presence of steam and a catalyst. These conditions help to facilitate the breakdown of larger hydrocarbons into smaller molecules like ethene.

To produce ethanol as economically as possible from the reaction between ethene and steam, several factors must be considered:

1. Temperature: A higher temperature increases the rate of reaction but can also lead to lower yields due to the exothermic nature of the reaction. A balance should be struck to maximize production.

2. Pressure: Increasing pressure favors the production of ethanol by shifting the equilibrium to the right, where there are fewer moles of gas. However, high pressure increases costs due to the need for stronger equipment.

3. Catalyst: Utilizing a catalyst can increase the reaction rate without affecting equilibrium, making production more efficient and cost-effective.

4. Compromise Conditions: A compromise must be reached between achieving a high yield and reducing costs (energy and material).

In conclusion, the operating conditions should aim for a moderate temperature and high pressure while employing a catalyst to optimize both yield and cost-effectiveness.

This process is called fermentation.

The reaction conditions needed to produce butanol from sugar solution by adding bacteria should include:

1. Warm Temperature: A temperature range of 25 °C to 45 °C is ideal for bacterial activity.
2. Anaerobic Conditions: The process should occur in an environment devoid of oxygen to favor the anaerobic fermentation pathways.

To calculate the number of moles of ethanol needed to travel 200 km, we first convert kilometers to meters:

200 km = 200,000 m.

The total energy required to travel 200 m is calculated as:

Total Energy = Distance × Energy per meter = 200,000 m × 1.95 kJ/m = 390,000 kJ.

Knowing that the energy content of ethanol is 1300 kJ/mol, we can find the number of moles needed:

Number of moles = Total Energy / Energy per mole = 390,000 kJ / 1300 kJ/mol = 300 moles.

Therefore, 300 moles of ethanol are needed.

The balanced equation for the complete combustion of butanol can be written as follows:

C₄H₁₀O + 6 O₂ → 4 CO₂ + 5 H₂O.