Organic Lab

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Melting point 1. What two effects do impurities have on the melting point of an organic compound? Soluble impurities affect the melting point of a solid in the following manner. a. The presence of an impurity in the molten compound reduces its vapor pressure thus lowering the melting point of the compound. b. Broaden the melting point range. 2. For what tow purpose are melting points routinely used a. To determine the identity of an organic solid. b. To determine the purity of an organic solid. 3. What effects on the measured melting point would you expect in each of the following cases? a) Presence of pieces of glass in the sample No effect. b) Presence of solvent within the crystals Melting point depression,…show more content…
To removed colored impurities by adsorption. 4. How are insoluble impurities removed during recrystallilzation ? Removed by hot gravity filtration . 5. How are soluble and insoluble impurities removed during recrystallization? Soluble impurities removed by suction filtration after cooling. Insoluble impurities removed by hot gravity filtration . 6. Why must the flask and funnel be heated before the hot solution is filtrated? To prevent pre-mature precipitation of the solid on the funnel or in the receiver. 7. Why fluted filter paper used for a hot filtration ? Allow the liquid to pass through it very quickly and give you a lot of surface area on which collect the solid “impurities” 8. Mention three prosperities a solvent should have to be suitable for recrystallization a particular organic compound? 1. purfied compound must be very soluble in hot solvent and almost insoluble in cold solvent. 2. It dissolves the impurities completely at room temperature. 3. The solvent must not react with substance to be purified. 4. Cheap, non-flammable and non toxic . 5. Volatile solvent (Low Boiling point).easily removed 6. It should have boiling point lower than the melting point of the solid to be purified. Extraction 1. What are the properties of a suitable solvent for the extraction of an organic solute from an aqueous solution? 1. Immiscible with first solvent. 2. Solubility of extracted solute in it

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