Physical Chemistry Lecture 3: Enthalpy

Change in enthalpy when one mole of a compound is formed from its elements.

Change in enthalpy when one mole of a substance is completely burned in an excess of air or oxygen.

Change in enthalpy when one mole of a substance dissolves in a specific amount of solvent at a given temperature.

Change in enthalpy

Heat content of a chemical system.

An equation that shows the amount of heat absorbed or released during a chemical reaction or physical process.

A reaction where heat is released to the surroundings.

A reaction where heat is absorbed from the surroundings.

Change in enthalpy, which represents the heat change at constant pressure.

The enthalpy change when 1 mole of a compound is formed from its constituent elements in their standard states.

The numerical values in a balanced chemical equation that represent the mole ratios of reactants and products.

The enthalpy change when a substance is completely burned in oxygen.

The physical forms (solid, liquid, gas, aqueous) of reactants and products need to be explicitly indicated.

Conditions under which enthalpy (ΔH) is measured.

Conditions under which the internal energy (ΔE) is measured.

The sum of a system's internal energy (E) and the product of its pressure (P) and volume (V).

The change in enthalpy during a reaction or process, calculated as the difference between the enthalpy of products and reactants.

The change in internal energy during a reaction or process at constant volume.

Conditions in which the pressure is held constant during a chemical process.

Conditions in which the volume is held constant during a chemical process.

Measurement of heat changes associated with chemical reactions

A property of a system that depends only on its current state, not on the path taken to reach that state.

The relationship between enthalpy change (ΔH), internal energy change (ΔE), pressure (P) and change in volume (ΔV) at constant pressure.

For reactions involving only solids and liquids, the change in volume (ΔV) is so small that PΔV is negligible, thus ΔH and ΔE approximately the same.

For reactions involving gases, the PΔV term becomes important, and ΔH and ΔE are different.

A reaction where heat is absorbed from the surroundings, increasing the system's temperature.

A reaction that releases heat to the surroundings, decreasing the system's temperature.

Change in enthalpy during a reaction. Enthalpy is a measure of thermal energy in a system.

No heat change occurs in the system; products and reactants have the same enthalpy.

Exothermic reaction; heat is released.

Endothermic reaction; heat is absorbed.

Change in internal energy in a system.

Change in the number of moles of gas during a reaction.

The work done by or on the system due to changes in pressure and volume.

Equation relating enthalpy change (ΔH) to internal energy change (ΔE) and pressure-volume work.

Processes that release heat to the surroundings.

Processes that absorb heat from the surroundings