Question

Define the following terms:
a) Enthalpy of reaction (∆rH)
b) Standard enthalpy of reaction (∆rH0)
c) Enthalpy of formation (∆fH) and standard enthalpy of formation (∆fH0)
d) Enthalpy of combustion (∆cH)
e) Calorific value of fuel
f) Enthalpy of fusion (∆fusH)
g) Enthalpy of vaporisation (∆vapH)
h) Enthalpy of sublimation (∆subH)
i) Enthalpy of solution (∆solH)
j) Hydration enthalpy (∆hydH)
k) Enthalpy of transition
l) Lattice enthalpy
m) Bond dissociation enthalpy (∆bH)
n) Enthalpy of neutralisation
o) Enthalpy of atomisation (∆aH)

Answer 1

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• For a chemical reaction, the enthalpy of reaction (ΔHrxn) is the difference in enthalpy between products and reactants; the units of ΔHrxn are kilojoules per mole. Reversing a chemical reaction reverses the sign of ΔHrxn.
• The standard enthalpy of reaction (denoted ΔHr⦵) is the enthalpy change that occurs in a system when matter is transformed by a given chemical reaction, when all reactants and products are in their standard states.
• The standard enthalpy of formation is a measure of the energy released or consumed when one mole of a substance is created under standard conditions from its pure elements. The symbol of the standard enthalpy of formation is ΔH f. = A degree signifies that it's a standard enthalpy change.
• Standard enthalpy of combustion (ΔH∘C Δ H C ∘ ) is the enthalpy change when 1 mole of a substance burns (combines vigorously with oxygen) under standard state conditions; it is sometimes called “heat of combustion.” For example, the enthalpy of combustion of ethanol, −1366.8 kJ/mol, is the amount of heat produced when
• The heat value of a fuel is the amount of heat released during its combustion. Also referred to as energy or calorific value, heat value is a measure of a fuel's energy density, and is expressed in energy (joules) per specified amount (e.g. kilograms).
• The enthalpy of vaporization (symbol ∆Hvap), also known as the (latent) heat of vaporization or heat of evaporation, is the amount of energy (enthalpy) that must be added to a liquid substance to transform a quantity of that substance into a gas.j
• The enthalpy of fusion of a substance, also known as (latent) heat of fusion is the change in its enthalpy resulting from providing energy, typically heat, to a specific quantity of the substance to change its state from a solid to a liquid, at constant pressure.
• The enthalpy of sublimation, or heat of sublimation, is the heat required to change one mole of a substance from solid state to gaseous state at a given combination of temperature and pressure, usually standard temperature and pressure (STP).
• The enthalpy of solution, enthalpy of dissolution, or heat of solution is the enthalpy change associated with the dissolution of a substance in a solvent at constant pressure resulting in infinite dilution. The enthalpy of solution is most often expressed in kJ/mol at constant temperature.
• Hydration energy is the amount of energy released when one mole of ions undergoes hydration. Hydration energy is one component in the quantitative analysis of solvation. It is a particular special case of water. The value of hydration energies is one of the most challenging aspects of structural prediction.
• Enthalpy of transition is the change in its enthalpy resulting from providing energy, typically heat, to a specific quantity of the substance to change its state from a solid to a liquid, at constant pressure
• The lattice energy of a crystalline solid is a measure of the energy released when ions are combined to make a compound. It is a measure of the cohesive forces that bind ions. Lattice energy is relevant to many practical properties including solubility, hardness, and volatility
• Bond enthalpy (which is also known as bond-dissociation enthalpy, average bond energy, or bond strength) describes the amount of energy stored in a bond between atoms in a molecule. Specifically, it's the energy that needs to be added for the homolytic or symmetrical cleavage of a bond in the gas phase.
• The enthalpy of neutralization is the change in enthalpy that occurs when one equivalent of an acid and a base undergo a neutralization reaction to form water and a salt. It is a special case of the enthalpy of reaction. It is defined as the energy released with the formation of 1 mole of water
• The enthalpy of atomization (also atomisation in British English) is the enthalpy change that accompanies the total separation of all atoms in a chemical substance (either a chemical element or a chemical compound). This is often represented by the symbol ΔatH or ΔHat.