The purpose of a separation scheme is to show, in the form of a simple flowchart, how a reaction product is isolated (separated) and purified from the mixture of product, by-products, and unreacted starting materials present at the end of a synthesis reaction.
Examples of separation methods are: distillation, extraction, filtration, decantation. In the laboratory, after you've completed one of these separations, you will have part of the mixture physically separated from another part (e.g., in filtration, a solid is contained in the funnel and the liquid filtrate is in the filter flask). As you look at the separation schemes, notice that the connecting arrows usually include a solvent or reagent that has been added to the product mixture at that point, and most importantly, some method of separating components of the mixture is indicated.
Also notice that some of the substances that are added aid in a physical separation only while other added substances actually react with one or more of the mixture components. For example, adding water to a mixture containing both ionic and organic compounds will preferentially dissolve the ionic substances so they can be extracted from the mixture. Adding an aqueous solution of sodium bicarbonate to a mixture containing acidic substances will result in the bicarbonate reacting with the acid in an acid-base reaction. The products of this last reaction can then be separated from the other components.
Another example is the procedure used to remove residual water from a reaction product. The "drying agent" is an anhydrous salt which, when it comes into contact with the residual water remaining from an aqueous extraction, will react with the water to form the hydrated salt. Thus, the substance is no longer MgSO4, but rather MgSO4.xH2O, where x is some number of water molecules incorporated into the crystal lattice. The hydrated salt is then separated from the organic liquid by a vacuum filtration. This should all be indicated explicitly in the separation scheme.
* When you write your separation scheme, draw the Lewis structures for each substance at least once. Thereafter, you can use normal chemical abbreviations. At no time should you use molecular formulas for organic compounds. For example, you can write "EtOH" for ethanol -- not C2H6O. This notation makes it easier to construct and read thhe scheme.
The manual or textbook will usually include possible by-products of a reaction. By-products should be included in the separation scheme to show how they are separated from the desired product.