Lab 2 POST-LABORATORY QUESTIONS used in this 1. Refined, white table sugar is su
ID: 1083753 • Letter: L
Question
Lab 2 POST-LABORATORY QUESTIONS used in this 1. Refined, white table sugar is sucrose that has been "recrystallized." Using methods you experiment, describe how you would purify crude sugar by recrystallization 2 You found that naphthalene is more soluble in petroleum ether than water. How do you account for this difference in solubility? 3. Solutions of hydrochloric acid caused the light bulb to glow brighter than solutions of acetic acid. How do you account for the difference in behavior between these two compounds? 4. Hexane is an organic solvent that has a density of 0.6603 g/cm3 at 20°C. If hexane is mixed with water, there is a separation of the two solvents into two layers. Why did this separation occur Which solvent would be on top? 5. A solute and a solvent are mixed together. What requirement would enable you to predict that the two substances would form a homogeneous solution?Explanation / Answer
1. Crude sugar can be purified by recrystallization. Water is used as a solvent for recrystallization. Dissolve crude sugar in minimal amount of water under warm conditions, filter the hot solution to remove insoluble impurities. Allow the solution to cool to room temperature whereby the crystals of pure sugar comes out of solution.
2. Naphthalene is a hydrocarbon and is a non-polar compound, therefore, it would dissolve preferably in a non-polar solvent such as petroleum ether which is also non-polar in nature. This is according to the rule of like-dissolves-like. So polar water solvent would dissolve polar compounds in it.
3. HCl is a strong electrolyte, that is it dissociates completely into H+ and Cl- ions in solution which carries electrons more efficiently and therefore light bulb glows brighter in HCl solution than the weak electrolyte acetic acid which dissociates into ions only to a small extent.
4. Hexane with a lower density than water would remain at the top of water. Hexane is a non-polar solvent and thus is immiscible with polar water solvent. There is no interaction between non-polar hexane and polar water system and therefore the two are not miscible with each other.
5. If the polarity of the solute and the solvent are similar, that is if both the solute and the solvent are polar or both are non-polar, they would make a homogeneous solution.
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