The table shows possible conditions and products for the cracking of alkanes - AQA - A-Level Chemistry - Question 8 - 2017 - Paper 3

To determine the correct row for the cracking of alkanes, we need to understand the conditions and the products associated with thermal and catalytic cracking.

1. Thermal Cracking: This process typically occurs at high temperatures (around 400-900°C) and can involve high pressures. It predominantly produces alkanes and alkenes but is less selective than catalytic cracking.

2. Catalytic Cracking: This occurs at lower temperatures (around 450-500°C) and slight pressure, using a catalyst, which allows for more selective production of branched alkanes and aromatics.

Analysis of Options:

• A: Thermal, high pressure - Incorrect. Thermal is generally associated with high temperatures, not necessarily high pressure.
• B: Thermal, slight pressure - Incorrect as thermal cracking typically involves high temperatures.
• C: Catalytic, slight pressure - Correct, as catalytic cracking occurs under slight pressure and produces branched alkanes and aromatics.
• D: Catalytic, high pressure - Incorrect, as catalytic cracking is normally not carried out under high pressure.

Therefore, the correct answer is C: Catalytic, slight pressure, mainly branched alkanes and aromatics.