What is the formula for calculating the number of moles of a gas?

The formula for calculating the number of moles of a gas is derived from the ideal gas law, which relates pressure, volume, temperature, and the number of moles of a gas. The correct formula, represented by the choice that involves volume divided by molar volume, indicates that the number of moles is determined by how much volume a certain amount of gas occupies relative to the volume that one mole would occupy at standard temperature and pressure (STP).

To understand this further, the molar volume of a gas at STP is approximately 22.4 liters. Therefore, when you divide the volume of the gas you have by this standard molar volume, you obtain the number of moles present. This relationship is particularly useful in stoichiometry and allows you to efficiently calculate the amount of gas in moles when given a specific volume.

In contrast, the other formulas involving PV/RT relate to the ideal gas law, where pressure (P), volume (V), temperature (T), and the ideal gas constant (R) are involved in calculating the number of moles. However, they do not directly correspond to the concept of dividing volume by molar volume, which is a straightforward method for finding moles based solely on the