Joule per mole

The joule per mole (symbol: J·mol⁻¹ or J/mol) is an SI derived unit of energy per amount of material. Energy is measured in joules, and the amount of material is measured in moles. For example, the Gibbs free energy is quantified as joules per mole.

Since 1 mol = 6.02214179×10²³ particles (atoms, molecules, ions, etc.), 1 joule per mole equals 1 joule divided by 6.02214179×10²³ particles, or (6.022×10^23 particles/mol), 1.66054×10⁻²⁴ joules per particle. This very small amount of energy is often expressed in terms of a smaller unit like the electronvolt (eV, see below).

Physical quantities measured in J·mol⁻¹ generally describe amounts of energy transferred during phase transformations or chemical reactions. Division by the number of moles makes it easy to compare between processes involving different amounts of material and between similar processes involving different types of materials. The meaning of such a quantity always depends on the context and, particularly for chemical reactions, depends on the (possibly arbitrary) definition of a 'mole'. for a particular process.

Kilojoule per mole

For convenience and because of the range of quantities involved, these quantities are almost always reported in kJ mol⁻¹ rather than J mol⁻¹. For example, the heats of fusion and vaporization are usually on the order of 10 kJ mol⁻¹, the binding energies are on the order of 100 kJ mol⁻¹, and ionization energies of the order of 1000 kJ·mol⁻¹.

1 kJ·mol⁻¹ equals 0.239 kcal·mol−1 or 1.04×10⁻² eV per particle. At room temperature (25°C, 77°F, or 298.15K) 1 kJ·mol⁻¹ equals 0.4034kBT{displaystyle k_{B}T}.

To convert kilocalories to kilojoules, multiply by a constant factor of 4.184.

Example: 1 kilocalorie = 1000 calories. 1 thermochemical calorie = 4.184 joules. 1 thermochemical kilocalorie = 4.184 kilojoules.

Physical quantities measured in kJ mol^-1:

• Steaming detail
• Entalpía de fusion
• ionization energy