GCE A/L Chemistry case studies
GCE A/L Chemistry · Put your knowledge to work in context.
The GCE Advanced Level Chemistry examination in Sri Lanka is the school-leaving and university-entrance qualification taken after the Ordinary Level, sat by students aiming for science, engineering, medicine, and related university courses. It is a national examination administered by the Department of Examinations, and this page is an independent study resource with no official affiliation. The GCE A/L Chemistry case studies are 5 cases and about 3,951 words.
1Spirit-burner combustion: how far can a school calorimetry result be trusted?
In a school laboratory, a candidate burns ethanol in a spirit burner beneath a copper can holding 50.0 g of water. The water temperature rises from 21.0 °C to 55.5 °C while the burner loses 0.92 g of ethanol.
808 words, about 4 min2Designing a pH 7.40 phosphate buffer and the tempting pH 6.00 wash
A technician must prepare 250 cm³ of a phosphate buffer of pH 7.40 for an enzyme assay run at 25 °C, using solid sodium dihydrogen phosphate (NaH2PO4, Mr = 120.0) and disodium hydrogen phosphate (Na2HPO4, Mr = 142.0). For H2PO4⁻ ⇌ HPO4²⁻ + H⁺, pKa = 7.20 at 25 °C.
721 words, about 4 min3Marble chips and acid: interpreting a mass-loss rate experiment
Marble chips (2.00 g, 1.0–1.5 mm) are added to 50.0 cm³ of 1.00 mol dm⁻³ hydrochloric acid at 25.0 °C in a conical flask standing on a balance. Carbon dioxide escapes and the mass loss is recorded every 30 s: time / s: 0, 30, 60, 90, 120, 150 mass loss / g: 0, 0.40, 0.72, 0.97, 1.06, 1.09 Some chips are still visible at the end.
862 words, about 4 min4Choosing a sacrificial anode for a buried steel pipeline
A steel pipeline buried in moist soil at pH 6.5 is protected by connecting blocks of a more reactive metal to it. The engineer must choose between magnesium (Mr 24.3, density 1.74 g cm⁻³) and zinc (Mr 65.4, density 7.14 g cm⁻³).
750 words, about 4 min5One tertiary bromide, two products: substitution versus elimination
A student has 10.0 g of 2-bromo-2-methylpropane (Mr = 137.0; bp 73 °C) and must make two compounds: 2-methylpropan-2-ol (Mr = 74.0; bp 82 °C) for an esterification, and 2-methylpropene (bp −6.9 °C) for a polymer study. The laboratory supplies 2.00 mol dm⁻³ NaOH(aq), 2.00 mol dm⁻³ NaOH in ethanol, ethanol, a fractionating column, and a cold trap.
810 words, about 4 min