Question 1: Define cracking in the context of crude oil refining.

Answer: Cracking is a chemical process that breaks down large hydrocarbon molecules in crude oil into smaller, more useful molecules like petrol and diesel.

Question 2: Explain the main difference between thermal cracking and catalytic cracking.

Answer: Thermal cracking uses high temperatures and pressures to break molecules, while catalytic cracking uses a catalyst to lower the energy required and improve efficiency.

Question 1: Describe what happens at a molecular level during catalytic cracking.

Answer: Hydrocarbon molecules adsorb onto the catalyst surface, where bonds are broken more easily, resulting in smaller hydrocarbons being formed.

Question 2: Identify two main products obtained from cracking of larger hydrocarbons.

Answer: Petrol (gasoline) and diesel.

Question 1: A barrel of crude oil contains 1000 liters of hydrocarbons. If cracking converts 70% of these hydrocarbons into petrol, how many liters of petrol are produced?

Answer: 700 liters

Question 2: If the energy required to crack 1 mole of a hydrocarbon is 150 kJ, how much energy is needed to crack 10 moles?

Answer: 1500 kJ

Question 1: List two safety precautions that should be taken when performing cracking experiments in a laboratory setting.

Answer: Wearing heat-resistant gloves and safety goggles; ensuring proper ventilation to avoid inhaling fumes.

Question 2: Identify one variable that can be controlled during a cracking experiment and explain its effect.

Answer: The temperature; increasing temperature generally speeds up cracking but may lead to unwanted by-products.

Question 1: A refinery reports that increasing catalytic cracker temperature from 500°C to 550°C results in a 15% increase in petrol yield but also increases the production of unwanted by-products. Explain the trade-off involved in adjusting this temperature.

Answer: Increasing the temperature can improve the efficiency of cracking and increase petrol yield, making the process more profitable. However, it also promotes the formation of unwanted by-products, which can require additional processing and increase costs. Therefore, the refinery must balance yield and product quality.

Question 2: Describe how cracking contributes to the availability of fuels like petrol and diesel for everyday use.

Answer: Cracking breaks down large hydrocarbons in crude oil into smaller, more useful fuels like petrol and diesel, increasing their availability for transportation, industry, and daily life.