ANS:D - all (a), (b) & (c)

Entrainment: Entrainment occurs when liquid droplets are carried upward with the vapor flow in the column. These liquid droplets contain components that should have been separated on the trays or plates within the column. Entrainment reduces the efficiency of the distillation process by causing mixing between the liquid and vapor phases, leading to reduced purity in the products.

1. Foaming: Foaming happens when bubbles form and accumulate on the trays or plates within the distillation column. Foam disrupts the normal flow patterns of vapor and liquid, hindering efficient separation. It can also cause liquid entrainment, as the foam bubbles may carry liquid droplets with them as they rise through the column. Foaming often occurs due to the presence of impurities, surface-active agents, or excessive agitation in the system.
2. Weeping and Dumping: Weeping refers to the unwanted downward flow of liquid from one tray to another without proper separation. This can occur when the liquid flow rate exceeds the capacity of the tray, leading to liquid bypassing the separation mechanisms and reducing efficiency. Dumping, on the other hand, involves a sudden release of liquid from a tray due to factors like hydraulic imbalance or sudden changes in operating conditions. Both weeping and dumping can disrupt the equilibrium established on the trays and result in decreased separation efficiency.

These phenomena can significantly impact the performance of a distillation column by reducing the purity of the products and increasing energy consumption. Effective design, operation, and troubleshooting techniques are employed to mitigate these issues and optimize the distillation process.