Guidelines for personal laboratory safety pg 5-8 Equipment Commonly used in Orga
ID: 1061302 • Letter: G
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Guidelines for personal laboratory safety pg 5-8 Equipment Commonly used in Organic Chemistry Laboratory pg 2 Know proper notebook techniques Technique: Melting Point Determination Expt. 1 What properties should an ideal melt point/range contain? Is melting point a physical or chemical property and why? Should a melting point/range be taken fast or slow? Why? If given a series of mixed melting points, be able to identify composition. If given a melting point range and the literature value, be able to assess the purity of the sample. Technique: Recrystallization Expt. 2 What is the purpose of recrystallization? What lab equipment is used? What is percent recovery and how is it calculated? Is it possible to have percent yield greater than 100%? Technique: Extraction Expt. 3 What is the purpose of extraction? What lab equipment is used? Partition Coefficients calculations pg 2 Example: 10 g of compound A in 100 ml of water...how many grams of compound A would be removed by four successive extractions with 25 mL portions of hexanes? How many mL of hexanes would be required to remove the same amount of A in a single extraction? Technique: Distillation (Part 1: Simple Distillation) Expt. 4-1 Why was a copper metal sponge used? Why is placement of thermometer important. Draw the apparatus and know names of each piece of glassware.Explanation / Answer
Technique : Melting point determination Expt1
1).The melting range of a pure organic solid is the temperature range at which the solid is in equilibrium with its liquid. The melting range of a compound is one of the characteristic properties of a pure solid. Melting points are sensitive to the purity of the organic compound, since the crystal lattice of the compound is disrupted by the presence of an impurity. The melting range is defined as the span of temperature from the point at which the crystals first begin to liquefy to the point at which the entire sample is liquid. Most pure organics melt over a narrow temperature range of 1-2ºC
2). Physical properties can be observed or measured without changing the composition of matter. Examples of physical properties are: color, smell, freezing point, boiling point, melting point, infra-red spectrum, etc. So melting point is a physical property.
3). While determining the melting point if we heat the sample too fast errors will come. Good results will obtain if the rate of heating be 1 to 2 degrees per minute. Going faster than 5 degrees per minute will give poor results
4). It is difficult to identify the composition
5). Yes. The melting point of a pure compound will exactly match with the reported value. So by comparing the experimental value and reported value we can judge the purity of the compound.
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