Answer: 3.625 L of oxygen gas will be required.
Step-by-step explanation:
We know that:
1 mole of a gas occupies 22.4 Liters of gas.
For the reaction of formation of water, the balanced equation follows:

By Stoichiometry of the reaction:
2 moles of hydrogen gas reacts with 1 mole of oxygen gas.
This means that 44.8 L of hydrogen gas reacts with 22.4 L of oxygen gas.
So, 7.25 L of hydrogen gas will react with = [tex]\frac{22.4L}{44.8L}\times 7.25L=3.625L[tex] of oxygen gas.
Hence, 3.625 L of oxygen gas will be required.