$5.$ The $\_\_\_\_\_\_\_\_\_$ coefficient is a dimensionless quantity that reflects how much a substance's fugacity deviates from its pressure.

$6.$ In phase equilibrium, the fugacity of each component in the liquid phase must equal its fugacity in the $\_\_\_\_\_\_\_\_\_$ phase.

$7.$ The $\_\_\_\_\_\_\_\_\_$ Equation is a graphical method used to estimate the fugacity coefficient of a substance.

$8.$ Activity coefficients are introduced in non$-$ideal solutions to account for interactions that deviate from $\_\_\_\_\_\_\_\_\_\text{'}$s law.