Q1: 'Cox' chart which is useful in the design of a distillation column (particularly suitable for petroleum hydrocarbons) is a plot of the

ANS:A - temperature vs. log (vapor pressure).

The "Cox" chart, also known as the "McCabe-Thiele equilibrium diagram," is a plot used in the design of distillation columns, especially for petroleum hydrocarbons. It is a graphical method for analyzing binary distillation systems. In the Cox chart, the horizontal axis typically represents the mole fraction of one component in the liquid phase, while the vertical axis represents the mole fraction of the same component in the vapor phase. The equilibrium curve, which represents the composition of the vapor phase in equilibrium with the liquid phase at various temperatures, is plotted on the Cox chart. Therefore, among the options provided, the most suitable description for the Cox chart is: vapor pressure vs. temperature.