Which of the following statement is/are correct?
I. The heat of solution is defined as the enthalpy change when one mole of solute is dissolved in excess of solvent so that further dilution does not bring any heat change at constant temperature and pressure.
II. Heat exchange between system and surrounding at constant volume is equal to change in internal energy.
III. Density, molar conductance and molarity are intensive properties.

All three statements are correct.

I. The heat of solution is defined as the enthalpy change when one mole of solute is dissolved in excess of solvent so that further dilution does not bring any heat change at constant temperature and pressure. This definition describes a specific condition where the dissolution process is complete, and no further heat change is observed upon further dilution.

II. Heat exchange between system and surrounding at constant volume is equal to change in internal energy. This statement describes the first law of thermodynamics, which states that the change in internal energy of a system is equal to the heat exchange between the system and its surroundings at constant volume, plus any work done by or on the system.

III. Density, molar conductance, and molarity are intensive properties. An intensive property is a property that does not depend on the amount or size of the system being measured. Density, molar conductance, and molarity are all examples of intensive properties. The density of a substance, for example, is the same regardless of the size of the sample being measured. Similarly, the molar conductance of a solution does not change with the size of the container in which it is placed, as long as the concentration of the solution remains the same.