Writing Symbols for Atoms
Magnesium has three isotopes with mass numbers 24, 25, and 26. (a) Write the complete chemical symbol (superscript and subscript) for each. (b) How many neutrons are in an atom of each isotope?
Give the complete chemical symbol for the atom that contains 82 protons, 82 electrons, and 126 neutrons.
CHEM 203 – Organic Chemistry I Separation of Organic Compounds by Acid-Base extraction techniques Introduction A commonly used method of separating a mixture of organic compounds is known as liquid-liquid extraction. Most reactions of organic compounds require extraction at some stage of product purification. In this experiment you will use extraction techniques to separate a mixture of an organic acid and a neutral compound. Organic acids and bases can be separated from each other and from neutral compounds by extraction using aqueous solutions of different pH values. Most organic carboxylic acids are insoluble or slightly soluble in water, but are highly soluble in dilute aqueous sodium hydroxide because the acid is deprotonated by the base producing the sodium carboxylate salt. The carboxylic acid can be selectively isolated by dissolving the mixture in an organic solvent that is immiscible with water, and then extracting the solution with sodium hydroxide. The basic aqueous solution containing the carboxylate salt is acidified, causing the sodium carboxylate salt to convert back to the carboxylic acid, which is not water soluble. The acid precipitate from the solution, as shown here. Organic bases (e.g., amines) that are insoluble in water can be separated by extraction with hydrochloric acid. Addition of HCl to the amine produces the corresponding ammonium salt, which is soluble in water but not in organic solvents. The amine can be recovered from the aqueous solution by treatment with a base, converting the ammonium salt back to the a