Final answer:
To determine the number of moles of water vapor in the gas, multiply the given volume by the conversion factor 1 mol/22.4 L.
Step-by-step explanation:
To determine the number of moles of water vapor in 12461 L of gas over water at 26 °C, we need to use the information that 22.4 L of a gas at STP (standard temperature and pressure) equals one mole.
Given that 22.4 L = 1 mol, we can set up a conversion factor: 1 mol gas / 22.4 L gas
By multiplying the given volume of gas (12461 L) by the conversion factor, we can calculate the number of moles of water vapor in the gas.