Question

Determine the reaction type for this chemical equation:

P4 + 3 O2 → 2 P2O3


single replacement

synthesis

decomposition

combustion

double replacement

Answer 1

Synthesis (combination). Two reactants, elemental phosphorus and oxygen, combine to form a single compound (P2O3).
Note: it is also an oxidation/combustion of phosphorus (reaction with O2), but the primary classification here is synthesis.