HKDSE Chemistry case studies
HKDSE Chemistry · Put your knowledge to work in context.
The Hong Kong Diploma of Secondary Education (HKDSE) is Hong Kong's senior secondary school-leaving qualification, administered by the Hong Kong Examinations and Assessment Authority (HKEAA). Chemistry is one of the Category A Senior Secondary elective subjects, alongside Biology, Physics, Chinese Literature, Literature in English and others. The HKDSE Chemistry case studies are 5 cases and about 2,879 words.
1Standardising a Vinegar Titration When One Run Disagrees
A student determines the ethanoic acid content of a commercial vinegar sample. She pipettes 25.0 cm3 of vinegar into a 250.0 cm3 volumetric flask and makes it up to the mark with distilled water.
627 words, about 3 min2Sacrificial Anodes on a Steel Pier: Zinc Versus Aluminium
A steel pier is protected from seawater corrosion by blocks of zinc bolted to the submerged structure. The zinc blocks are replaced when about 60% of their mass has been lost.
585 words, about 3 min3Using Initial Rates to Find a Rate Equation for H2O2 Decomposition
A student studies the decomposition of hydrogen peroxide, 2H2O2(aq) → 2H2O(l) + O2(g), using potassium iodide as a catalyst. In each run, the total volume of the reaction mixture is made up to 50.0 cm3 with distilled water and kept at 25 °C.
616 words, about 3 min4A White Solid: When the Chloride Test Proves Nothing
A white solid was recovered from a laboratory bench. A student carried out the following tests.
547 words, about 3 min5Esterification Equilibrium: Adding Water Does Not Push the Reaction Right
Ethyl ethanoate is formed by the reversible reaction: CH3COOH(l) + C2H5OH(l) ⇌ CH3COOC2H5(l) + H2O(l) A student mixes 0.50 mol of ethanoic acid with 0.50 mol of ethanol in a sealed 1.00 dm3 flask at 25 °C, using a little concentrated sulfuric acid as catalyst. At equilibrium, the flask contains 0.33 mol of ethyl ethanoate.
504 words, about 3 min