Final answer:
The coefficients when balancing the chemical equation P4 + O2 --> P2O5 are P4 + 5O2 --> 2P2O5.
Step-by-step explanation:
The coefficients when the chemical equation P4 + O2 → P2O5 is balanced are:
P4 + 5O2 → 2P2O5
The equation is balanced when there are 4 molecules of phosphorus (P4) reacting with 10 molecules of oxygen (O2) to produce 2 molecules of tetraphosphorus decoxide (P2O5).