Question

Why is it important to open the stopcock on the separatory funnel when extracting from one phase (say, organic phase,) into another phase (say, aqueous phase)?

Answer 1

When we are doing workup for any reaction with water two layers are formed one is organic layer and another one is aqueous layer. So to collect them seperateky we always open stopcock because once one layer will come out we can stop the stopcock immediately so that second layer will remain in seperating funnel. If we will open upside stopper and will try to take layers separately they will always come as a mixture so we to avoid this we are alwyas using stopcock. This stopcock we are also using to release pressure while doing workup.