a)
Interpretation:Effect of unnecessarily large volume of solvent in recrystallization process should be determined.
Concept introduction:Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
b)
Interpretation:No use of fresh cold solvent to wash crystals in recrystallization process should be explained.
Concept introduction:Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
c)
Interpretation:Use of fresh hot solvent to wash crystals in recrystallization process should be explained.
Concept introduction:Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
d)
Interpretation:Effect of use of large quantity of decolorizing carbon should be determined.
Concept introduction:Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
e)
Interpretation: Effect of formation of crystals by solidified mass of oil separated from hot solution should be determined.
Concept introduction: Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
f)
Interpretation: Effect of acceleration of crystallization by immediate placement of flask of hot solution in ice-water bath should be determined.
Concept introduction: Recrystallization is technique that is used for purification of organic compounds. This process includes dissolution of solid in specific solvent at high temperature and then crystals are made again by process of cooling. Temperature of crystals is decreased to allow impurities to remain in solution only.
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Chapter 3 Solutions
EBK EXPERIMENTAL ORGANIC CHEMISTRY: A M
- A student is trying to perform a single solvent recrystallization of compound X using methanol. He observed that compound X is insoluble in methanol at room temperature and also insoluble at boiling temperature. Is methanol a good recrystallization solvent? A. Yes, you want to only dissolve the impurities and the sample should remain undissolved. B. No, you need a solvent which fully dissolves the sample only at room temperature so that it can crystallize in the ice bath. C. No, you need a solvent which dissolves the sample only at boiling temperature for selective crystallization upon cooling. D. Yes, you don't want the solvent to fully dissolve the sample at both temperatures so that it will crystallize in the cooling step. A student obtained a supersaturated solution in the recrystallization experiment. Which of the following methods should he/she perform to induce crystal growth? (Can select more than 1) A. Add a crystal of pure acetylsalicylic acid B. Place the solution in an ice…arrow_forwardWhich of the following is NOT TRUE about simple distillation? a. The greater the difference in the boiling points of the components, the better the separation. b. The less volatile component boils first and travels along the condenser. c. It can be applied to mixtures with components boiling below 150°C. d. A sand bath can be used in place of a water bath to provide even heating of the flask.arrow_forward5. Discuss how melting points of the impure sample and recrystallized sample could have been used to determine the success of your recrystallization and identity of your unknown.arrow_forward
- Which of these is NOT true of a good recrystallization solvent? Which of these is NOT true of a good recrystallization solvent? a) The compound is insoluble in the solvent when it is cold. b) The solvent boiling temperature is at least 40 °C. c) The solvent has many impurities. d) The compound is soluble in the solvent when it is hot.arrow_forwardWhich of the following could DECREASE the amount of the recovered crystals in the purification by recrystallization experiment? Collecting the recrystallized benzoic acid by filtration using a pre-weighed filter paper. Using a long-stemmed funnel in the hot filtration step. Cooling the filtered solution rapidly. Washing the recovered crystals using hot solvent. a. II, III b. II, IV c. II, III, IV d. I, II, III, IVarrow_forward3. When separating hexanes and heptane (both organic liquids), which would be the most suitable means of separation? a. recrystallization b. steam distillation Your answer: c. fractional distillation d. simple distillationarrow_forward
- You will be completing the extraction of caffeine with dichloromethane and water. In which solvent will the caffeine be found after the layers are mixed, and is this the top or bottom layer? A. Dichloromethane - top layer B. Dichloromethane - bottom layer C. Water - top layer D. Water - bottom layerarrow_forwardWhich of the following should be done if there is no recrystallization due to the unsaturation of the solution? (mixed solvent recrystallization) a. Crystal seeding b. Scratching the inner walls or bottom of container c. Further boiling of solvent d. Adding small amount of samplearrow_forward52. In an extraction using two-solvent system, methanol can be used to decrease the solubility of the non-polar component. This technique in reducing the solubility of organic solutes by saturating the mixture is called "Salting-out effect". O "Saturation Process" O "Distillation Process"arrow_forward
- If we are recrystallizing a PURE compound, what will happen to the sample if we cool the solution rapidly, i.e., placing it on an ice bath without cooling it first at room temperature? Note: kindly disregard the effect of rapid cooling on the container used.arrow_forwardWhat physical property determines which solvent sinks to the bottom when performing a liquid-liquid extraction? A. Refractive Index B. Solubility C. Density D. Boiling Pointarrow_forwardHow was the precipitate obtained after filtration? a. By drying the precipitate on the filter paper using a desiccator. b. By charring the filter paper and igniting the product in a crucible. c. By redissolving in hydrochloric acidarrow_forward
EBK A SMALL SCALE APPROACH TO ORGANIC LChemistryISBN:9781305446021Author:LampmanPublisher:CENGAGE LEARNING - CONSIGNMENT