Substances that ignite when combined create a _________ reaction.

Substances that ignite when combined create a _________ reaction.

• A. Combustion
• B. Hypergolic
• C. Pyrolytic
• D. Exothermic

Answer: (B)

Hypergolic reactions occur when two substances ignite automatically upon contact, without an external ignition source. That spontaneous ignition on mixing is exactly what the statement describes. Combustion is the general burning process and usually requires an ignition source or a proper fuel-oxidizer mix, not necessarily happening just by touching the components. Pyrolytic refers to decomposition by heat alone, not ignition from mixing. Exothermic means the reaction releases heat, which can happen in many processes and doesn’t specify ignition upon contact. So the term that best fits substances igniting when combined is hypergolic.

Hypergolic reactions occur when two substances ignite automatically upon contact, without an external ignition source. That spontaneous ignition on mixing is exactly what the statement describes. Combustion is the general burning process and usually requires an ignition source or a proper fuel-oxidizer mix, not necessarily happening just by touching the components. Pyrolytic refers to decomposition by heat alone, not ignition from mixing. Exothermic means the reaction releases heat, which can happen in many processes and doesn’t specify ignition upon contact. So the term that best fits substances igniting when combined is hypergolic.