At a given temperature and pressure how does the magnitude of the heat of vaporization of a substance compare with that of its heat of condensation?

it is equal and opposite.

To understand the magnitude of the heat of vaporization and the heat of condensation of a substance at a given temperature and pressure, we need to first define these terms.

The heat of vaporization (also known as the enthalpy of vaporization) is the amount of heat energy required to convert a given quantity of a substance from a liquid to a gas phase, at a constant temperature and pressure. It represents the energy needed to break the intermolecular forces holding the molecules in the liquid phase and convert them into the gaseous phase.

The heat of condensation, on the other hand, is the amount of heat energy released when a substance changes from a gas to a liquid phase at a constant temperature and pressure. It represents the energy that is released when the vapor molecules come together and form intermolecular forces to transition into the liquid phase.

At a given temperature and pressure, the magnitude of the heat of vaporization is generally greater than the magnitude of the heat of condensation. This is due to the fact that it requires more energy to overcome the intermolecular forces and break the liquid phase bonds to transition into the gaseous phase. In other words, it takes more energy to separate the molecules in the liquid phase than it does to condense the gas molecules back into the liquid phase.

The difference in magnitudes between the heat of vaporization and the heat of condensation can be explained by considering the physical properties of the substance, such as the strength and nature of its intermolecular forces. Stronger intermolecular forces result in a higher heat of vaporization, indicating a greater amount of energy required to break those forces. Conversely, weaker intermolecular forces result in a lower heat of vaporization, indicating less energy is needed for vaporization.

It is important to note that the values of the heat of vaporization and the heat of condensation are specific to each substance and can vary depending on the temperature and pressure conditions. To determine these values for a particular substance at a given temperature and pressure, experimental data or thermodynamic calculations are typically required.