Answer:
2.5 mole of O2
Step-by-step explanation:
From the equation we see that we need 5 molecules of oxygen to react with 2 molecules of C2H2.
This means that 5 moles of oxygen molecules are needed to completely react with 2 moles of C2H2, because a mole is a unit of particle count.
From that we can infer that to react with 1 mole of C2H2 we need half of 5 moles of oxygen - so 2.5 mole of oxygen molecules.