$6.$ Describe the criteria for phase equilibrium in a binary system and how composition affects it$.$

$7.$ How does the phase rule apply to a system with multiple phases in equilibrium?

$8.$ What methods are used to calculate the fugacity of pure components in both gaseous and liquid states?

$9.$ Explain the concept of fugacity coefficient and its role in thermodynamics.

$10.$ How are fugacity charts constructed, and what information can be obtained from them?