Final answer:
Approximately 2.5670 moles of H2 gas are present in 57.5 liters at standard temperature and pressure, calculated by dividing the volume by the molar volume of 22.4 L/mol.
Step-by-step explanation:
When determining the number of moles of H2 gas present in a given volume at standard temperature and pressure (STP), we can use the molar volume concept, which states that one mole of any gas at STP occupies 22.4 liters. In this case, we are given that H2 gas occupies 57.5 liters at STP.
To find the number of moles, we divide the total volume of the hydrogen gas by the molar volume:
Moles of H2 = Volume of H2 / Molar volume at STP
= 57.5 L / 22.4 L/mol
= 2.5670 mol (rounded to four significant figures)
Therefore, there are approximately 2.5670 moles of hydrogen gas present in 57.5 liters at STP.