A-Level Chemistry PAG 6: Synthesis Of An Organic Solid Questions And Answers | Latest Version | Graded A+

A-Level Chemistry PAG 6: Synthesis Of An Organic Solid Questions And Answers | Latest Version | Graded A+ **Question:** What are the necessary equipment and materials for the synthesis of benzoic acid via reflux and recrystallization? **Answer:** Required equipment includes: - Measuring cylinder (10 cm3) - Dropping pipettes - Quickfit apparatus: pear-shaped or round-bottom flask, Liebig condenser and tubing - 250 cm3 beaker - Glass rod - Anti-bumping granules - Apparatus for filtration under reduced pressure (Buchner funnel and Buchner flask) - Filter papers - Balance accurate to two decimal places - Boiling tube - Melting point apparatus - Capillary tubes - TLC plate - Sample tube and lid - Bunsen burner - Distilled water - Ethanol - Methyl orange - Methyl benzoate - HCl (2 mol dm−3) - NaOH (2 mol dm−3) **Question:** What is the method for Part 1 of the synthesis procedure for benzoic acid? **Answer:** Here's the method for Part 1 - Preparation: 1. Add 2.0 cm3 of methyl benzoate into a pear-shaped flask. Add 10 cm3 of sodium hydroxide, 10 cm3 of ethanol, and a few anti-bumping granules. Attach to a condenser. 2. Heat the flask gently for 5 minutes, then reflux for another 15 minutes. 3. Allow the flask to cool, then transfer the solution to a beaker, rinsing the flask with distilled water to ensure no product is lost. 4. Add ten drops of methyl orange indicator and acidify with hydrochloric acid. Solid benzoic acid will crystallize. 5. Filter the mixture under reduced pressure to obtain impure benzoic acid. **Question:** What is the method for Part 2 - Recrystallization and melting point determination of benzoic acid? **Answer:** 1. Transfer the impure benzoic acid to a boiling tube. 2. Purify the benzoic acid by recrystallization using a minimum volume of boiling water in a water bath. 3. Cool the boiling tube and contents, then filter the purified benzoic acid under reduced pressure onto a watch glass. Allow it to dry. 4. Weigh the dry product to determine yield. 5. Determine the melting point of the pure benzoic acid