Answer:
B₂
Step-by-step explanation:
The limiting reactant is always a reactant. You can determine which reactant is limiting by identifying which has the smaller mole-to-mole ratio with the product. This ratio can be found via the coefficients of the balanced reaction.
4 A₂ + 3 B₂ ---> 6 AB
4 moles A₂
------------------ = mole-to-mole ratio A₂/AB
6 moles AB
3 moles B₂
------------------ = mole-to-mole ratio B₂/AB
6 moles AB
Since the mole-to-mole ratio between B₂ and AB is smaller, B₂ must be the limiting reactant.