Question

QUESTIONS FOR m-Dinitrobenzene lab (Nitration of the aromatic molecules)

2) During the washing of the "crude" Product, the filtrate was checked with pH paper as it dripped from the funnel. Why was this done rather then check the filtrate that collected in the suction flask? Explain Fully.

Answer 1

1. First of all, Washing of the crude product was done to remove impurities espacially acid impurities present in the reaction mixture or in the crude product.

2. When we start washing in the begining, these acid impurities get collected as filtrate in the suction flask. Which means that the filtrate in the suction flask is acidic.

3. Now when repeated (2nd or 3rd) washing is done, you have to check whether the product is free from acid using PH paper by checking the fresh filtrate coming from the funnel and not the filtrate that gets collected in the suction flask (because the filtrate in suction flask will be acidic in nature and will give us wrong interpretation).

This is reason why the fresh filtrate was checked with pH paper as it dripped from the funnel and not the filtrate that collected in the suction flask.