Chemical reactor (10) and method for cracking are disclosed. A process fluid is accelerated with axial impulse impellers (40A, 40B) to a velocity greater than Mach 1 and, in turn, generating a shock wave (90) in the process fluid by decelerating it in a static diffuser (70) having diverging diffuser passages (72). Temperature increase of the process fluid downstream of the shockwave cracks or splits molecules, such as hydrocarbons entrained in the process fluid, in a single pass, through a unidirectional flow path (F), within a single stage, without recirculating the process fluid for another pass through the same stage. In some embodiments, a system involving at least two turbomachine chemical reactors (110) may provide multiple successive stages of one or more axial impulse impellers (40A, 40B), paired with a diverging passage, static diffuser (70).