Assertion: The extensive properties of a single pure substance will not only depend upon the number of moles of the substance present but also on any two of the three variables. Reason: Any extensive property if expressed as per mole or per gram becomes an intensive property.

Here, assertion and reason are both true but the reason does not explain the assertion. For example, consider the extensive property volume given 5 moles of 2 O if the volume is asked, we need other 2 variables – pressure and temperature to calculate volume. Thus assertion is true. Mass (expressed in grams or moles) is an extensive property. Thus an extensive property when expressed as per mole or per gram becomes the ratio of 2 extensive properties thereby becoming intensive.