Answer:
Decomposition reaction.
Step-by-step explanation:
2HI —> H₂ + I₂
From the above equation, we can see clearly that HI undergoes a reaction to produce H₂ and I₂ which are the elements that make up HI.
Therefore, the equation illustrated above is a decomposition reaction because HI breaks into H₂ and I₂
NOTE: Decomposition reaction is a reaction in which a compound splits or breakdown into two or more simple elements or compound.