Which equation represents the relationship for calculating enthalpy changes?

The relationship expressed in the equation "q = mcΔT" accurately describes how to calculate the heat energy (q) absorbed or released by a substance when its temperature changes. In this equation, 'm' represents the mass of the substance, 'c' is the specific heat capacity (a measure of how much heat energy is needed to raise the temperature of a unit mass of the substance by one degree Celsius), and 'ΔT' is the change in temperature (final temperature minus initial temperature). This formula is particularly useful in calorimetry studies where one examines the heat transfer that occurs during a physical or chemical process.

The application of this equation allows for practical calculations in various scenarios, such as determining the amount of heat required to achieve a certain temperature change in a specific amount of substance. Hence, it provides a direct way to relate the thermal properties of a material to changes in energy.

In contrast, the other equations have different contexts: "ΔH = mcΔT" suggests a relationship that combines concepts of enthalpy and heat transfer, which isn't generally accurate; "ΔH = q + w" focuses on the first law of thermodynamics regarding the internal energy of a system; and "q = nRT" is specifically related