Final answer:
Using the molar volume of a gas at STP, which is 22.4 liters per mole, we determine that 57.5 liters of H2 gas at STP is equivalent to approximately 2.57 moles of hydrogen.
Step-by-step explanation:
The question concerns the determination of the number of moles of hydrogen gas (H2) present in a given volume of gas at Standard Temperature and Pressure (STP). To find the number of moles from the volume, we utilize the molar volume of a gas at STP, which is 22.4 liters.
Given that H2 gas at STP occupies 57.5 liters, we can calculate the number of moles (n) using the formula:
n = Volume at STP / Molar Volume at STP
n = 57.5 L / 22.4 L/mol
n ≈ 2.57 moles of H2
Therefore, 57.5 L of H2 gas at STP contains approximately 2.57 moles of hydrogen.