WBCHSE HS Chemistry case studies
WBCHSE HS Chemistry · Put your knowledge to work in context.
The WBCHSE Higher Secondary Chemistry course is the Class 11–12 chemistry programme set by the West Bengal Council of Higher Secondary Education, usually taken by students who have finished Madhyamik and are aiming at undergraduate science, engineering, medical or pharmacy admissions. It is a two-year school-leaving qualification rather than a professional licence, and it is assessed through a written paper plus a separately marked practical examination with internal and external assessment. The WBCHSE HS Chemistry case studies are 5 cases and about 3,129 words.
1Hydride Anomalies: Separating Electronegativity from Hydrogen Bonding
In a practical class, students are given a table of measured data for group 16 and group 15 hydrides and asked to account for the anomalies rather than simply quote them. The recorded values are: boiling points - H2O 373 K, H2S 213 K, H2Se 232 K, H2Te 269 K; NH3 240 K, PH3 185 K, AsH3 211 K.
673 words, about 3 min2Ammonia Reactor at 700 K: When a Positive ΔG° Still Gives Product
In a fertiliser plant the shift engineer is reviewing the ammonia synthesis section. For N2(g) + 3H2(g) ⇌ 2NH3(g) the plant manual quotes ΔH° = −92.4 kJ mol⁻¹ and ΔS° = −198 J K⁻¹ mol⁻¹, effectively constant between 300 K and 900 K.
604 words, about 3 min3Four 0.100 mol kg⁻¹ Solutions and a Benzoic Acid Anomaly
An examiner gives a class four aqueous solutions, each prepared to be 0.100 mol kg⁻¹ in solute: (A) glucose, (B) NaCl, (C) CaCl2 and (D) ethanoic acid (Ka = 1.8 × 10⁻⁵). Students must arrange them in order of boiling point without measuring.
646 words, about 3 min4Two Cells, One Diluted Half-Cell: Judging Feasibility with the Nernst Equation
A student assembles two cells at 298 K and records the emf. Cell I is Zn(s) Zn²⁺(0.10 M) Cu²⁺(0.0010 M) Cu(s), for which E°cell = 1.10 V; the measured value is close to 1.04 V.
572 words, about 3 min5Four Unlabelled Bottles and Two Overconfident Claims
Four unlabelled bottles from a school store cupboard contain butanal, butan-2-one, phenol and ethanoic acid. A student is allowed four reagents: 2,4-dinitrophenylhydrazine (2,4-DNP), Tollens' reagent, aqueous NaHCO3 and neutral FeCl3 solution, plus alkaline iodine solution borrowed from the next bench for one confirmatory test.
634 words, about 3 min