Match the following industrial processes with the catalysts used:
Cracking of hydrocarbons – Fe
Each process is paired with its appropriate catalyst, enhancing the reaction's efficiency. For example, Ostwald's process uses \( \text{CuCl}_2 \) to produce nitric acid from ammonia.
The following graph indicates the system containing 1 mole of gas involving various steps. When it moves from Z to X, the type of undergoing process is: