User guide

Critical temperature
Reported in Kelvin, this is the temperature above which a gas cannot be liquefied, regardless of the pressure applied.
Critical volume
Reported in cm
3
/mol, this is the volume occupied by one mole of a substance at the critical temperature and pres-
sure.
Exact mass
This is the sum of the masses of the individual isotopes in the molecule. For example, the exact mass of water con-
taining two hydrogen-1 (1H) and one oxygen-16 (16O) is 1.0078 + 1.0078 + 15.9994 = 18.0106. The exact mass of
heavy water, containing two hydrogen-2 (deuterium or 2H) and one oxygen-16 (16O) is 2.014 + 2.014 + 15.9994 =
20.027.
Formal charge
This is the charge assigned to an atom in a molecule, assuming that electrons in a chemical bond are shared equally
between atoms, regardless of relative electronegativity.
The formal charge of any atom in a molecule can be calculated using the formula:
FC=V-N-B/2
Where ‘V’ is the number of valence electrons of the atom in isolation (atom in ground state); ‘N’ is the number of non-
bonding electrons on this atom in the molecule; and ‘B’ is the total number of electrons shared in covalent bonds with
other atoms in the molecule.
Freezing point
The freezing point for the structure at 1 atm. Units Kelvin.
Gibbs free energy
Reported in KJ/mole, Gibbs free energy is defined as:
which is same as:
Where:
U is the internal energy (SI unit: Joule)
p is pressure (SI unit: Pascal)
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