Rate law chemistry

Question

Given the reaction C₂H₄ + 3O₂ —> 2CO₂ + 2H₂O and the rate constant k = 3.408 L/(mol x S),

what is the rate of production of CO₂ when C₂H₄ = 0.15 M and O₂ = 0.08 M?

Answer 1

The rate of production of CO₂ will be twice the rate of disappearance of C₂H₄ and 2/3 the rate of disappearance of O₂.

Based on the units for the rate constant (L/mol*s), we can tell this is a SECOND order reaction. Without additional data, not sure how we know if it is 2nd order in C₂H₄ and zero order in O₂, or 1st order in both, or 2nd order in O₂ and zero order in C₂H₄(not likely), all of which would obey 2nd order kinetics.

If 2nd or in C₂H₄: rate = k[C2H4] = 3.408 M^-1s^-1 (0.15 M)² = 0.0767 M/s x2 = 0.153 M/s for CO₂

Maybe someone else will weigh in on how to know how to write the rate law when we don't know the order for each reactant.