views updated May 08 2018

fugacity (f) A measure of the tendency of a gas to escape or expand, used in calculations of chemical equilibrium. Fugacity (fi) is the pressure value needed at a given temperature to make the properties of a nonideal gas satisfy the equation for an ideal gas, i.e. fi = γiPi, where γi is the fugacity coefficient, and Pi is the partial pressure for the component i of the gas. For an ideal gas, γi = 1.