appreciating the world of chemistry and biochemistry : Know what lipstick is composed of!!

appreciating the world of chemistry and biochemistry : Know what lipstick is composed of!!: Lipstick is a cosmetic people apply on their lips to promote attractiveness. But what does it is made up of? it is composed of insoluble dye...

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How to write a Forensic Case Study: Murder of Junko Furuta

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Roles of Sodium Carbonate when Extracting Caffeine from Tea Leaves

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A student failed to add sodium carbonate (Na 2 CO 3 ) when extracting caffeine from tea leaves with hot water. Though, high yield of caffeine was produced. The crystals melted at temperatures between 202  and 214 degree  Celsius. Explain. This happened because sodium carbonate did not interfere with the caffeine content of the tea leaves. Sodium carbonate (which is a base) deprotonates the phenolic hydroxyl group (-OH) (acidic) of tannins rendering them anionic. Hence, making them highly soluble in water, but parsimoniously soluble in methylene chloride. So, if sodium carbonate is not added when extracting caffeine with hot water, the extracted caffeine would also contain tannins. Additionally, sodium carbonate is added during the extraction to keep caffeine (an alkaloid which is an organic base)  in a free base form. It prevents caffeine from reacting with available acid available, which may lead to the formation cation. It reacts with a phenolic h...
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Arrhenius equation: Increasing temperature increases the rate reaction

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The rate of reaction of a particular reaction often increases as one increase the temperature. However, how can this belief be proved using Arrhenius equation? According to the Arrhenius equation, the rate constant (k) is obtained by the ratio of Ea to RT, in which Ea denotes required energy while RT is the available thermal energy. The Arrhenius Equation is given by: k=Ae - (Ea/RT) When Ea is larger, it results in slower reactions. On the other hand, when RT is large, it leads to faster rate of reaction. Larger Ea gives smaller rate constant k, but larger RT produces larger rate constant (k). Larger rate constant increases the rate of reactions.  By using Arrhenius equation, one can easily see that when the temperature is increased, the rate constant will also increase. Let us consider these two scenarios. In the first scenario, Ea=120,000 Joules/mole, R=8.31 mol -1 K -1 , and K=373K.In the second scenario, Ea=120,000Joules/mole, R=8.31 mol -1 K -1 , and K...
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