Q1: In Mcabe-Thiele method, at infinite reflux ratio

ANS:C - both the operating lines coincide with the diagram.

In the McCabe-Thiele method, at infinite reflux ratio: Both the operating lines coincide with the diagram. At infinite reflux ratio, the rectifying section of the distillation column is effectively operating as an equilibrium stage. In this scenario, the composition of the liquid leaving each stage in the rectifying section is the same as the composition of the vapor in equilibrium with it. This means that the operating lines for both the rectifying section and the stripping section coincide with the equilibrium curve on the McCabe-Thiele diagram. The number of plates required for separation is determined by the intersection of the equilibrium curve with the diagonal operating line. However, at infinite reflux ratio, the operating line coincides with the equilibrium curve, so the number of plates required cannot be determined using this method. The overhead product may not necessarily be maximum at infinite reflux ratio. The product composition is determined by the location of the feed on the McCabe-Thiele diagram relative to the operating lines, and the operating lines coincide with the equilibrium curve at infinite reflux ratio. Therefore, the correct statement is: Both the operating lines coincide with the diagram.