Enthalpy

Question 1

What is defined as the reference point for enthalpy?

Answer 1

Only changes in enthalpy, rather than absolutes, can be measured

Chemical elements in their standard states at 298.15 K are defined as having 0 enthalpy

Question 2

What is the standard enthalpy?

Answer 2

The enthalpy change for a chemical reaction in which all reactants and products are in their standard states

Abbreviated as ΔH°

For a reactionm it is the sum of the heat of formation of the products minus the heat of formation of the reactants

Question 3

What is the standard enthalpy of formation?

Answer 3

The enthalpy change for the reaction that produces 1 mol of the compound from its elements in their standard states

Question 4

What is enthalpy?

Answer 4

Enthalpy is the change in heat associated with a given physical or chemical process carried out at constant pressure. It is equivalent to the change in internal energy plus whatever change in energy is necessary to maintain constant pressure

Bottom line: It’s essentially a “corrected” internal energy that accounts for the effects of constant pressure

So, the enthalpy of a reaction is the heat transfer that would be associated with that reaction, accounting for the differences in internal energy of the reactants and products and work

More convenient to use than actual internal energy because it can be measured through calorimetry