Question

2. IN BULLET FORMAT, outline and describe THREE (3) separation TECHNIQUES (recrystallization, extraction, and synthesis) (not equipment or chemical/physical properties) that have been used in these experiments and include ONE specific example from the experiments for each. Highlight the key properties that facilitate those techniques.

Answer 1

separation process is a method that converts a mixture or solution of chemical substances into two or more distinct product mixtures.^[1]At least one of results of the separation is enriched in one or more of the source mixture's constituents.

RECRYSTALISATION-

• Recrystallization is a method of purifying a compound by removing any impurities tha is mixed with original pure compound or complex.
• Generally, this technique used to purify solid compounds. Because Solids have a property to be more soluble in hot solvents than in cold ones. During this recrystallization process, an impure solid compound is dissolved in a hot liquid until the solution is saturated, and then the liquid is allowed to cool. Thus a compound of relatively pure and almost without any impurity is formed. The pure compound will tak the form of crystal and the impurities that are present will remain in the solution and will not be incorporated into the growing crystals.
• A successful recrystallization depends on nature of solvent. The compound must be soluble in the hot solvent and insoluble in the same solvent when it is cold. For the purpose of recrystallization, we generally consider 3% w/v rule i.e if 3 g of a compound dissolves in 100 mL of a solvent, it is considered soluble. In choosing a solvent, the bigger the difference between hot solubility and cold solubility, the more product recoverable from recrystallization.
• Again the rate of cooling determines the size and quality of the crystals: rapid cooling favors small crystals, and slow cooling favors the growth of large and generally purer crystals.
• Example- Pure sugar and salt are obtained through recrystallization in Industries. This is done by dissolving the solute (sugar or salt) in a solvent (water) and heating the solution. After the solution crosses its saturation stage, them it is cooled down and crystals of poyr sugar or salt is obtained. Later is is given defferent shapes for commercial purpose.

2-EXTRACTION-

• Extraction is a method to separate a desired substance when it is mixed with others. Generally this methos is used to separate a liquid liquid mixture or solid-solid phase. The components of the mixtures are generally insoluble with each other.
• This method use two imiscible phases ( that do not mix, like oil and water) to separate the substance from one phase into the other.
• In this process the mixture is brought into contact with a solvent in which the one compound of the mixture ( generally our desired product) should be soluble, and the other substances present are insoluble. Thus we separate the solution of our desired compound through separating funnel and the in soluble part either remains in the funnel or separated out to another .
• Ex-Separation of Alcohols

3- SYNTHESIS

• Chemical synthesis,is the construction of complex chemical compounds from simpler ones. It is the process by which many substances specially important for our day-to-day life are obtained. Here a naturally unavailable or less available compound is extracted or synthesized from a naturally occuring substances.
• In industry, synthesis is used to make products in large quantity. Like manufacture of synthetic drugs, mixtures containing variable proportions of several compounds usually arise. Here the removal of the desired drug from the rest of the mixture is important. and thus through separation proess the undesired products are separated.