Red Seal Welding Practice Exam

What gas would generate the most heat for a preheat flame?

1. Acetylene

2. Hydrogen

3. Propane

4. Methane

The correct answer is: Propane

Propane would generate the most heat for a preheat flame because of its molecular structure. Propane consists of three carbon atoms and eight hydrogen atoms, giving it a higher number of bonds that can be broken during combustion. This results in a higher heat release compared to the other options, such as acetylene (which contains only two carbon atoms) and hydrogen (which has a diatomic molecular structure). Methane, while also having four hydrogen atoms like propane, has only one carbon atom which limits the number of bonds that can be broken, leading to a lower heat release. Therefore, propane is the most efficient choice for generating heat in a preheat flame.