Q1: The feed to fractionating column is changed from saturated vapour to saturated liquid. If the separation and reflux ratio remains unchanged, the number of ideal stages will

ANS:A - increase

If the feed to a fractionating column is changed from saturated vapor to saturated liquid, and if the separation and reflux ratio remain unchanged, the number of ideal stages in the column will increase. When the feed is changed from saturated vapor to saturated liquid, it means that the feed composition has shifted towards the more volatile components. As a result, the composition of the vapor phase entering the column will be richer in the more volatile components compared to the composition of the vapor phase in the original scenario where saturated vapor was used as the feed. With the richer feed composition of more volatile components, the number of theoretical stages required for separation increases. This is because a higher number of theoretical stages are needed to achieve the same degree of separation between components when the feed composition is richer in the more volatile components. Therefore, the number of ideal stages in the column will increase when the feed is changed from saturated vapor to saturated liquid, assuming the separation and reflux ratio remain unchanged.