A-LevelChemistryAnalytical techniquesOct/Nov 2024Paper 5 Q113 Marks
A student uses the following method to determine the percentage by mass of the painkiller aspirin, C9H8O4(s), in some tablets. step 1 Grind five tablets into a powder. step 2 Use a weighing boat to accurately weigh by difference approximately 0.4 g of powdered tablets into a pear-shaped flask containing anti-bumping granules. step 3 Add 25 cm³ of aqueous 1 moldm¯³ sodium hydroxide, NaOH(aq), to the pear-shaped flask, forming mixture A. step 4 Reflux mixture A for 20 minutes. step 5 Allow mixture A to cool and then filter into a small beaker. Label the filtrate solution B. step 6 Add 30cm³ of alkaline aqueous iodine to solution B and leave to stand for 1 hour. A precipitate, C, (C6H2I2O)2(s), will form. step 7 Filter the resulting mixture under reduced pressure. Wash the residue, C, with a small volume of cold distilled water. step 8 Allow solid C to dry. step 9 Weigh solid C and record its mass. Alkaline aqueous iodine is irritating to the skin and eyes.
✓ Correct Answer
The correct answer is —. This question tests the candidate's understanding of analytical techniques within the Chemistrysyllabus. The examiner's mark scheme requires...
📋 Examiner Report & Trap Analysis
Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
🔒
Unlock the Examiner's Answer
Sign up for free to reveal the correct answer, the official mark scheme breakdown, and the examiner trap analysis for this question.
Sign Up Free to Unlock →Join thousands of Cambridge students already using Oracle Prep