MCQ Detailed View

In physical chemistry, the concept of effective volume is commonly used in gas calculations. The effective volume refers to the volume occupied by the gas molecules themselves, excluding the space between molecules. In most standard calculations, the effective volume is taken for 1 mole of gas.

According to the ideal gas law (PV = nRT), the volume of 1 mole of an ideal gas at standard temperature and pressure (STP) is 22.4 liters. Using 1 mole as a reference simplifies calculations and allows chemists to apply constants directly in formulas. It also standardizes comparisons of different gases under the same conditions.

Other options are incorrect. Volumes for 2 moles, 3 moles, or 5 moles are simply multiples of 1 mole, but the standard practice in physical chemistry is to refer to 1 mole when discussing effective volume. This approach is widely used in experiments, theoretical calculations, and in deriving molar volume, density, and kinetic energy relationships.

Using 1 mole of gas also allows for easy application of Avogadro’s principle, which states that equal volumes of gases at the same temperature and pressure contain an equal number of molecules. By standardizing calculations on 1 mole, the relationships between pressure, volume, temperature, and number of particles are more straightforward.

Understanding the effective volume for 1 mole of gas is essential for students studying gas laws, thermodynamics, and physical chemistry. It ensures accurate calculation of molar properties, densities, and reaction stoichiometry involving gases.

Thus, in gas calculations, the effective volume is usually taken for 1 mole of gas, forming a fundamental concept in physical chemistry and laboratory practices.