PSEB SS Chemistry case studies
PSEB SS Chemistry · Put your knowledge to work in context.
The Punjab School Education Board (PSEB) Senior Secondary (Class 12) Chemistry examination is the board-level subject examination taken by Class 12 candidates in Punjab board schools, including regular and Open School candidates. PSEB came into existence through a legislative enactment in November 1969, and its Vidhan Sabha amended the Board's Act in 1987 to grant it autonomy; the Board sits at Vidya Bhawan, Phase-8, SAS Nagar (Mohali), Punjab. The PSEB SS Chemistry case studies are 5 cases and about 3,447 words.
1Daniell cell EMF that will not match the Nernst equation
A Class XII group is asked to verify the Nernst equation for the Daniell cell at 298 K. They prepare Zn Zn²⁺(0.10 M) Cu²⁺(0.10 M) Cu and read 1.10 V on a digital voltmeter, exactly the standard value.
690 words, about 3 min2Iodination of propanone: a timing error that inverts a reaction order
A student studies the iodination of propanone in aqueous hydrochloric acid at 298 K, following the disappearance of the iodine colour to a visual endpoint. Each run uses 25.0 cm³ of freshly mixed solution.
722 words, about 4 min3Identifying an unknown C₄H₈O when one test is contaminated
A colourless liquid, boiling at 79–80 °C, is shown by combustion analysis to have molecular formula C₄H₈O. A student runs three tests in the same test tube: (i) 2,4-dinitrophenylhydrazine reagent gives an immediate orange precipitate; (ii) Tollens' reagent, warmed for 10 minutes, gives no silver mirror, but a faint grey film appears at the rim of the tube, which had earlier been used for a glucose test and rinsed only with tap water; (iii) iodine in sodium hydroxide gives a yellow precipitate with a characteristic sweet smell.
647 words, about 3 min4A discordant titration reading caused by an air bubble
A student prepares a standard solution by dissolving 0.630 g of oxalic acid dihydrate (H₂C₂O₄·2H₂O, M = 126 g mol⁻¹) in distilled water and making the volume up to 250.0 cm³. Portions of 25.0 cm³ are titrated with sodium hydroxide solution of unknown concentration, using two drops of phenolphthalein.
728 words, about 4 min5Mohr's salt with a yellow-brown crust: recrystallise or discard?
A student prepares Mohr's salt by dissolving 2.80 g of FeSO₄·7H₂O (M = 278 g mol⁻¹) in 20 cm³ of water with 2 cm³ of dilute sulphuric acid, warming gently, then adding 1.40 g of ammonium sulphate (M = 132 g mol⁻¹). The solution is concentrated and cooled, and 3.10 g of pale-green crystals is collected.
660 words, about 3 min